If you have troubles getting enough sleep during the night, or staying asleep, you may be suffering from a sleep disorder. Unfortunately, many people all over the world wake up at night and are not … Read more

Written by:


, Sleep Researcher
Last Updated: Mon, January 23, 2023
Fact checked by:

Marko Jevtic

, Sleep Specialist

If you have troubles getting enough sleep during the night, or staying asleep, you may be suffering from a sleep disorder. Unfortunately, many people all over the world wake up at night and are not able to return to sleep. Some of them even wake up in the morning and feel like they haven’t slept at all. If these things happen to you regularly, it would be an excellent idea to consult your doctor. The chances that a medical disorder is interfering with your body and isn’t letting you get a good night’s sleep are high. 

What are Sleep Disorders? 

Sleep disorder is a medical condition that prevents us from getting restful sleep. As a consequence, we feel tired and dysfunctional during the day. According to research, more than 70 million Americans suffer from a sleep disorder. There are around 80 sleeping disorders types, and some of them are much more common than others. If we are sleep-deprived, we are at risk of developing severe medical problems that can even reduce our lifespan. Getting a bad night’s sleep occasionally is nothing to worry about, we have all been there, and it is not a reason to panic. However, if you have a consistent pattern of sleep deprivation, it may be a sign of a disorder that requires attention. In this case, it would be wise to consult your doctor and explain your symptoms. 


It is the most common sleep disorder, and almost half of the population experiences its symptoms occasionally, whereas about 10% of all people suffer from chronic insomnia. It is characterized by difficulty falling asleep, waking up too early, and having troubles going back to sleep. It can either occur by itself or be associated with other medical conditions. If it is short-term, it is also known as acute insomnia, whereas if it lasts for a long time it is called chronic insomnia. Most common symptoms of this sleep disorder include feeling unrefreshed after waking up, lack of energy, daytime sleepiness, depression, concentration difficulties, impulsive behavior, forgetfulness, and decreased quality of life. 

Sleep Apnea 

Sleep apnea is also quite common, and it can be potentially dangerous. It occurs when a sleeper’s breathing is interrupted, and there are two types: 

  • Obstructive Sleep Apnea 
  • Central Sleep Apnea 

Obstructive sleep apnea is more common, and it occurs when a sleeper’s breathing stops for a few seconds during the night due to obstructions in the airways. This blockage occurs when the throat’s soft tissue relaxes and collapses into the airways, thus blocking oxygen from reaching the lungs. Partial obstruction results in snoring, whereas full blockage results in gasping sounds. Some of the symptoms of this condition include fatigue, snoring, restlessness during the night, daytime sleepiness, and problems with concentrating. 

On the other hand, when it comes to central sleep apnea, airways are not blocked, and oxygen can get to the lungs, but the brain fails to tell the person’s body to breathe. It is related to the central nervous system, and people with this disorder wake up during the night and sometimes gasp for air. 


It is a neurological disorder that occurs when the brain is not able to control its sleep cycle. People with this condition can suddenly fall asleep during the day without any control, for example during a conversation, and experience daytime sleepiness and sudden muscle weakness. Some of the symptoms of narcolepsy include cataplexy, sleep paralysis, hallucinations, and disturbed nocturnal sleep. 

Restless Leg Syndrome 

This disorder causes an intense, persistent, and irresistible need to move legs, or sometimes other body parts, usually while lying down in bed or sitting. It falls into the category of sleep disorders as it usually occurs in the evening and makes falling asleep and staying asleep difficult. It is associated with irritability, daytime sleepiness, and lack of concentration. The exact cause of the restless leg syndrome is not familiar, but experts believe that it is hereditary. Its symptoms can be reduced by regular exercise, avoiding alcohol and caffeine, and prescribed medication in severe cases.  


Bruxism is also known as teeth grinding, and it affects almost 45 million people in the United States. According to experts, most common causes of this disorder are anxiety and excessive stress. Many Americans are under a lot of stress regularly, and it is not surprising that so many people are affected by this condition. If you have a headache in the morning, after waking up, or a sore jaw, it may be a sign that you are suffering from this problem. If this is the case, you can schedule a consultation with your dentist and get a mouth guard and avoid chewing anything that is not food. 


It is usually caused by the lack of sleep, fever, illness, or some medications. It happens during deep sleep, and it results in walking or performing other actions while the person is asleep. Sleepwalking affects children more than adults. If you or your kids are suffering from this disorder, it may be a good idea to reduce the intake of liquids a couple of hours before going to bed. 

If you ever got behind the wheel while feeling sleepy, you should know that you are not alone. Unfortunately, drowsy driving is a major problem in the US, and studies show that around 60% of … Read more

Written by:


, Sleep Researcher
Last Updated: Wed, June 24, 2020
Fact checked by:

Marko Jevtic

, Sleep Specialist

If you ever got behind the wheel while feeling sleepy, you should know that you are not alone. Unfortunately, drowsy driving is a major problem in the US, and studies show that around 60% of people did it at least once, and approximately one-third of people have fallen asleep at the wheel. Driving while feeling tired or drowsy may seem harmless, but it actually has severe consequences. No one knows the exact moment when sleep comes over their body. Therefore, you can quickly get into an accident and hurt yourself and others.

It is important to know that sleep deprivation has similar effects on your body as drinking alcohol. For example, when it comes to drowsy driving vs. drunk driving, being awake for 18 hours will make you drive like you have a BAC of 0.05%. To be clear, by law, 0.08% is considered drunk. If you haven’t slept for 24 hours, it’s like you have a BAC of 0.10. Drowsy driving mostly occurs when a driver didn’t get enough sleep, but it can also happen due to medications, shift work or untreated sleep disorders.

infographic on drowsy driving

What Is Drowsy Driving?

Drowsy driving is also known as driver’s fatigue, and it occurs when an individual is too tired to operate a motor vehicle. Due to this, the driver puts himself and others at risk. Some of the most common causes of drowsy driving are inadequate sleep, untreated sleeping disorders such as narcolepsy and sleep apnea, shift work, driving without making regular breaks and the use of sedatives, hypnotics and other medications that may negatively affect your alertness and induce sleepiness.

The effects of driver’s fatigue can vary from person to person, but most of them have slower reaction times and experience short-term memory loss while driving. Drivers can also sometimes drive aggressively.

Who Is at Risk for Drowsy Driving?

Every driver is at risk, but the issue is more common among certain groups.

Young Drivers

Inexperience combined with sleepiness and tendency to drive at night particularly puts at risk young males aged 16 to 25.  Sleep deprivation is another crucial factor. Most adults require seven to eight hours of quality sleep per night, but young adults require at least nine in order to achieve the same levels of functionality. However, an average adult gets only between 5 to 7 hours of sleep per night.

Young adults are encouraged to develop a healthy sleep schedule and to avoid alcohol and electronics at night to reduce the risks of drowsy driving. Inadequate sleep, tobacco, alcohol consumption and using electronic devices at night are one of the leading causes of sleep deprivation among individuals aged from 16 to 25.

Shift Workers

Shift work is as any work schedule that falls outside the standard work time of 9 am to 5 pm. Shift work may include night shifts, double shifts, or rotating shifts. In most cases, shift work is done where round-the-clock personnel is needed, such as in law enforcement and healthcare.

There are ways shift workers can reduce the risks of drowsy driving. For example, ride sharing will reduce their time behind the wheel each week. Also, long or overtime shifts should be avoided if they plan on driving long miles.

Commercial Drivers

Commercial drivers typically drive high miles, and at night, and due to this, they are particularly at risk for fall-asleep crashes. In order to decrease the risk of drowsy driving, commercial drivers shouldn’t operate their vehicles between 12 am to 6 am, and 2 pm to 4 pm because these are the period when most people get sleepy.  It is essential for them to take regular breaks, napping for at least 20 minutes and then allowing an extra 15 minutes to wake up. Power naps can help them a lot to restore energy, and increase their alertness.

Ride Sharing Service Providers

Although companies such as Uber and Lyft have regulations which involve their drivers to take regular breaks, they often work a second job which further increases their sleep debt.

Business Travelers

Business trips typically involve long journeys, in the case of international travels, and when you always have to adjust to the local time, it may affect your circadian rhythm and sleep cycle. The transition period or jet lag can especially be tricky and cause sleepiness.

To prevent or lower the risks of drowsy driving, business travelers should go to and from airports using car services. The effects of jet leg can also be reduced by gradually adjusting to the local time of the place you’re going to stay in. It is best to try to follow a sleep schedule that aligns with the time zone of your destination. Avoiding alcohol, smoking, and caffeinated beverages will also help to ease the effects of jet lag.

People with Untreated Sleep Disorders

Many sleep disorders can cause drowsiness. The most common sleep disorders that cause sleepiness are insomnia, sleep apnea and narcolepsy. A driver with an undiagnosed sleep disorder is at high risk of causing or being involved in a motor vehicle accident. For example, people with untreated obstructive sleep apnea are seven times more likely to fall asleep behind the wheel. Insomnia also increases fatigue.

Am I too Drowsy to Drive?

Same as drunk driving, drowsy driving makes it very hard to pay attention to the road and slows down your reaction time. Although sleep deprivation has similar effects on your brain as drinking alcohol, drowsy driving and drunk driving don’t always look the same on the road. A drunk driver may drive slowly and try to react, while a sleepy driver can nod off while still going very fast. Since sleep deprivation significantly slows down your reaction time, drowsy drivers won’t always break when something happens right in front of them.

The best way to prevent drowsy driving is to learn to recognize its signs. If you believe your fatigue level may be impacting your driving, here are some of the warning signs of drowsy driving you should look out for, no matter whether you are the driver or a passenger.

  • Inability to focus
  • Constantly yawning
  • Heavy eyelids
  • Bobbing your head
  • Drifting from your lane
  • Missing signs and turns

If you notice such behavior, it is vital to safely pull over the car and take a 20-minute nap. Also, buy a cup of coffee to stay more alert. If there is another driver in the car, let him or her to drive instead of you. If you are driving long miles, you should drive during your most alert period of the day and take regular breaks. These precautions seem simple, but they can help a lot to lower the risk of falling asleep behind the wheel and causing a drowsy driving accident.

Ways to Keep Yourself Up While Driving – Drowsy Driving Prevention

The best ways to prevent drowsy driving is to get some sleep. Before driving long miles, you have to get enough sleep and take breaks every few hours to rest. By learning to recognize signs of drowsiness and fatigue, you could avoid driving sleep deprived.

Avoid Driving

If you know your circadian rhythm is generally unstable or naturally drowsy, you have to avoid operating a vehicle, especially if you plan to drive for long miles.

Caffeinate Wisely

Never forget that coffee and other caffeinated beverages are not a replacement for sleep! Coffee and energy drinks can temporarily help you stay alert and improve your focus, but keep in mind that these effects last only for 30 minutes, and also require around half an hour to kick in.

Sleep Tight

Before going on a long road, get a good night’s sleep! This is the best way to ensure you won’t feel tired or drowsy on the road.

Drive Together

In most cases, drowsy driving accidents are caused by drivers who were driving alone. Therefore, if you are going on a long trip, bring a friend with you. A recent UCLA study found that bringing a friend can significantly decrease your chances of falling asleep at the wheel. Also, if your passenger has a license, he can replace you once you become sleepy.

Take a Break

When you need to get a nap, use a rest stop. A rest stop is a safe space to park your car and take a nap, grab a bite, and similar. Consuming a caffeinated beverage may also help you to stay alert. However, you should keep in mind that coffee and energy drinks will make you feel refreshed only for 15 to 20 minutes. Never forget that caffeine is not a replacement for sleep.

Check Your Meds

If you take medications regularly, it’s important to read the warning labels and see if they might affect your alertness or cause sleepiness. Medicines don’t have to be particularly prescribed for sleep disorders in order to induce drowsiness. Medication types such as narcotic pain relief pills, antidepressants, tranquilizers, antihistamines, and muscle relaxants can trigger sleepiness.

Bring in Some Fresh Air

Being in stuffy car interiors can easily make us sleepy. So, getting plenty of fresh air can also help to increase your alertness. Make sure to occasionally open the car windows or adjust the vent controls to bring in some fresh air.

Listen to Music

Listen to music, especially if you are driving alone. Rather than listening to loud music, we recommend listening to energetic music. This is also one of the way to prevent falling asleep while driving.

Drive with the Sun

Whenever possible, drive during the day, or even better, when the sun rises. Sun will stimulate melatonin production and your circadian rhythm, keeping you more awake and alert during the day. Sunlight stimulates your brain and will also extend your reaction time while at the wheel. Lastly, natural sunlight is an excellent source of vitamin D, which can help you sleep better at night.

Is Driving While Drowsy Illegal?

Driver’s fatigue can put you in jail. In most states, there isn’t a law that specifically relates to drowsy driving, but it’s mostly considered as a form of reckless driving, similar as driving under the influence of alcohol or drugs.

By acting as a responsible driver and educating yourself about the risks and warning signs of drowsy driving, you will avoid being a part of the 328,000 drowsy driving accidents that occur every year. The NHTSA and the CDC estimate that 109,000 of those crashes results in injuries, while 6,400 result in death. Also, don’t forget that we mentioned sleep-deprived driving is very similar to driving under the influence. Being awake for 24 hours straight is equal to a BAC of 0.10%, and that significantly higher that the legal limit of 0.08% in all US states.

A new study investigates how sleep deprivation impacts the way we perceive food smells, increasing the desire for foods rich in sugars and fat.

Written by:


, Sleep Researcher
Last Updated: Sun, March 1, 2020
Fact checked by:

Marko Jevtic

, Sleep Specialist

Sleep deprivation is bad for you for several reasons. It directly affects your body’s ability to repair itself, and it increases the chances of developing many health conditions such as heart diseases, diabetes, fatigue, and many more. But lack of sleep also makes people crave foods rich in sugar and fat.

When we are sleep deprived, we often go for junk food, and it can lead to weight gain and additional health problems. Scientists from Northwestern University wanted to investigate this link and find out what is the reason behind the desire for calorie-dense food choices following a sleepless night.

A new study hints that your nose may be the reason for junk food cravings. Sleep deprivation affects the olfactory system, which leads to a sharper perception of food smells. In addition, the communication between brain centers responsible for receiving food signals breaks down, which is why fries, donuts, and other junk food options seem like the best idea.

When certain parts of the brain aren’t getting proper signals, the brain may try to overcompensate by choosing energy-dense food. The researchers wanted to investigate why there is such a breakdown of communication between different brain regions.

Previous research has identified molecules called endocannabinoids (ECs) that are important for how the brain responds to odors, and they also play an important role in feeding behavior. When we are sleep deprived, there is an increased level of endocannabinoids in our blood. That is why these molecules were the logical suspect for investigation of this sudden change of eating behavior.

To investigate, researchers examined how sleep deprivation influenced food choices and how levels of an endocannabinoid called 2-oleoylglycerol (2-OG) changed. They tested 25 healthy adults with normal body mass index. Divided into two groups, participants experienced either usual or short sleep periods. After that, researchers analyzed 2-OG levels, food choices, and fMRI scans to see how sleep deprivation impacted brain connectivity.

Interestingly, when sleep-deprived people were given a choice to pick what they want to eat, they chose higher energy food like donuts, potato chips, and chocolate chip cookies. Sleep deprivation was also linked to higher levels of 2-OG.

Patients also underwent an fMRI scan before the buffet to help researchers understand how different odors affected signaling between brain regions. Interestingly, the piriform cortex, which is the first cortical brain region to receive olfactory signals, showed that food smells were perceived more strongly than non-food odors in sleep-deprived patients.

But that is not all.

The fMRI scans showed increased activity in the piriform cortex when sleep deprived patients encountered food odors. Source: Northwestern University

The piriform cortex sends signals to another region called the insular cortex, which is responsible for food intake and feelings of satiety. But when subjects were sleep-deprived, this connection was weaker, and it was also linked with an increase in 2-OG levels.

In conclusion, a lack of sleep influences the endocannabinoid system, which then affects different brain areas, and the result is an increased preference for energy-packed foods. The statistics show an alarming rate of sleep deprivation and obesity in the US, and these findings could help scientists to develop new ways of battling both things at once.



A new study looks into the relationship between sleep duration, mental health, cognitive performance, and brain structures in children.

Written by:


, Sleep Researcher
Last Updated: Sat, February 22, 2020
Fact checked by:

Marko Jevtic

, Sleep Specialist

Since childhood is the time when our central nervous systems develop, it is essential to make sure that children have everything they need during this time. That includes proper nutrition, physical and mental engagement, happiness, and, lastly, enough sleep.

Sleep is essential for proper cognitive functioning. It is well known that lower sleep duration is correlated with cognitive and mental health problems in adults. However, a large scale analysis of this correlation has lacked in children.

A new 2020 study wanted to analyze the impact of sleep duration on psychiatric and cognitive problems, and also see how it impacts different brain structures.

Researchers from the University of Warwick investigated over 11,000 children aged 9-11 from the Adolescent Brain Cognitive Development (ABCD) consortium. All the children came from the US with a wide range of geographic, ethnic, socioeconomic, and health backgrounds.

Behavioral measurements were used to obtain sleep duration, cognitive, and mental health assessments. Researchers also looked at structural MRIs to see if there were any changes in central nervous system composition in relation to sleep duration.

After statistical analyses, researchers found that the feelings of anxiety, depression, and impulsive behavior were negatively correlated with the sleep duration in participants. The same could be said with cognitive performance. Interestingly, the mental well being of parents was also negatively correlated with the amount of sleep their children were getting.

Looking at the neural imaging, researchers noticed a trend of lower brain volumes, especially in particular areas such as temporal, prefrontal, and orbitofrontal cortex, inferior and middle temporal gyrus, precuneus, and supramarginal gyrus.

Different brain areas affected by sleep. Source: University of Warwick.

After one year, a follow up with around half the initial participants showed depressive symptoms were correlated with shorter sleep duration even at that time. Since there is a complex link between sleep and mental health, we often see sleep disturbances in people with depression and anxiety. And it can be hard to break from that circle since mental health problems make it harder to maintain good sleep hygiene, and a lack of proper rest makes these conditions worse.

The biggest problem is that the majority of children don’t get enough sleep on school nights. Inappropriate screen time, the use of electronics before bedtime, inadequate school schedule, too much homework, and other activities can all impact your child’s rest. However, you should try your best to teach them the importance of sleep.

One of the coauthors, professor Edmund Rolls stated that children who slept for less than 7 hours on average expressed 53% more behavioral problems and had a 7.8% lower cognitive score than children who slept 9 to 11 hours. These numbers should highlight just how essential sleep is for both mental health and cognitive performance.

Although we need that sleep is vital, especially in the developing period, researchers admit that we need more studies to discover the underlying mechanisms for these links.

A new study shows that odor cues such as rose scent during learning and sleep improve vocabulary learning and test performance in 6th-grade students.

Written by:


, Sleep Researcher
Last Updated: Wed, February 19, 2020
Fact checked by:

Marko Jevtic

, Sleep Specialist

Learning during sleep has been a dream of many people for a long time. And even though some tried to learn Spanish, Chinese, or some other language by listening to lessons during sleep, they quickly found out that this method was not really useful. Even though sleep is essential for learning, it can not replace the learning effort.

However, a new study from the University of Freiburg shows it could be possible to optimize sleep and achieve more efficient learning.

The team of researchers wanted to assess the importance of odor cues during learning, sleep, and testing, on memory formation in school children. Some previous studies performed in laboratory conditions showed that odors could be a potent stimulus for memory consolidation during sleep. However, this new study wanted to explore how this hypothesis would hold in everyday conditions.

The study was conducted in 6th-grade healthy German students in their home and school environment. To see how odor impacts learning English vocabulary, researchers used rose scent as an odor cue. They divided the students into four groups

  1. The control group didn’t receive any intervention.
  2. The second group had a rose scent present while they were studying and sleeping.
  3. The third group had a rose scent present while learning and taking a test.
  4. The final group had a rose scent present while learning, sleeping, and taking a test.

The results surprisingly showed that the students remembered vocabulary much better with a rose scent. In fact, the students who were exposed to rose scent during learning and sleep showed a 30% increase in learning success compared to the control group. There was no difference between the second group where the fragrance wasn’t present during testing and the last group where it was present during all three phases. The researchers published these findings in the Nature Group’s Open Access journal Scientific Reports.

These findings suggest that a simple fragrance stick could be used for improving learning efficiency. It highlights the importance of odor cues in memory acquisition and consolidation. And if something so simple could be this efficient, everybody could boost their learning ability with ease.

However, there are a few limitations to this study. The participating students went to two different schools, meaning different teachers, classes, and tests. That could very well be a reason for some of the result differences. Also, there was no control over other environmental factors. Students were responsible for studying, and the use of scented sticks and their reports may not reflect these parameters objectively. That is why scientists perform these experiments in a lab, where they can control all the factors, but this study provides valuable insights nevertheless.

This could be a significant step towards making learning more efficient and improving the effect of sleep on memory formation.


A new study from Hokkaido University shows the role of MCH neuron activity during REM sleep in forgetting new information and maintaining brain plasticity.

Written by:


, Sleep Researcher
Last Updated: Sun, January 26, 2020
Fact checked by:

Marko Jevtic

, Sleep Specialist


The link between sleep, memory, and learning has been puzzling scientists for decades. It is clear that the memory forming process is closely related to sleep, and you wouldn’t be able to learn anything without it. But the mechanism behind how it all works is still a great mystery.

A new study from Hokkaido University in Sapporo, Japan, indicates that REM sleep is not only essential for learning, but it could be responsible for our ability to actively forget. It appears that forgetting things isn’t a random process at all, and neurons control it via certain hormones.

We are bombarded with millions of stimuli and new information every day. It would be impossible to remember all of this, which is why your brain must learn to recognize what’s essential and what’s not. Unimportant stuff gets discarded, and our brains don’t get overloaded. And it all happens during REM sleep.

Rapid eye movement or REM sleep is a sleep stage when most dreams occur, especially vivid ones. Scientists have long hypothesized that dreaming is important for memory by sending signals through specific pathways and strengthening neural circuits. But now, this new study on mice indicates that REM sleep could be the time when our brain decides what is not important, and activates mechanisms to forget that information actively.

Some scientists like Francis Crick – the co-discoverer of double-helix DNA structure, have hypothesized about the role of sleep, especially REM phase, in our ability to get rid of the excess information. But before this study, we had no idea about the mechanism of how the brain prunes certain synapses involved in learning.

A team of Japanese and US researchers was particularly interested in neurons producing melanin-concentrating hormone (MCH), which is known to play a role in the control of appetite and sleep. It turns out that the majority of MCH neurons (52.8%) in the hypothalamus are active during REM sleep. Around 35% fire during waking hours, while 12% are active during both states. And it seems that these MCH cells send inhibitory signals to specific memory centers like the hippocampus. 

To test the effects of MCH cell activity, researchers used different genetic tools to turn them on or off and see what kind of impact it would have on memory. They were particularly interested in the retention of new information before it had the time to be incorporated into long-term storage. 

And the results surprised them, as turning on MCH neurons had a negative impact on memory retention, and mice performed worse on memory tests. On the other hand, when MCH neurons were shot down, memory test results improved. That was only effective when managing MCH neurons during REM sleep. Turning them on and off when awake or during other sleep stages had no impact on memory retention. One of the authors, Dr. Kilduff, explained this by hinting that the activation of MCH cells could be to prevent the content of dreams from storing into long term memory. 

Researchers plan to investigate how these new findings could help us learn more about memory-related conditions such as Alzheimer’s, as well as sleep disorders. One thing is sure; sleep remains one of the essentials for a good memory!

Scientists have identified miRNA molecules that correlate with sleep duration in children and adolescents. Possible blood tests for assessing sleep hygiene.

Written by:


, Sleep Researcher
Last Updated: Sun, January 26, 2020
Fact checked by:

Marko Jevtic

, Sleep Specialist

Since sleep is essential for the growth and development of children, a lot of people are worried that their young ones aren’t getting enough rest. Insufficient sleep can lead to many health problems, including diabetes, increased blood pressure, and chances of developing many conditions. And even though sleep observation can give as a good idea about their sleep quality, it is highly subjective, and not entirely reliable.

But now, it seems like scientists have found a way of assessing sleep hygiene in children with a simple blood test. 

A new study published in the journal of Experimental Psychology by the Physiological Society looked into certain markers in blood and how they correlated with sleep duration in children and adolescents. 

A team of Italian researchers investigated 111 normal-weight children based on their body mass index. All participants came from eight European countries, including Italy, Spain, Germany, Belgium, Cyprus, Sweden, Estonia, and Hungary, and they were divided into two groups based on their self reported sleep habits.

The short sleeping group included children and adolescents who slept less than their minimal daily recommendation, which is 9 hours for children under 13 years and 8 for teenagers. The normal sleeping group consisted of children and adolescents who met their daily minimum sleep requirements.

Then scientists analyzed micro RNA (miRNA) blood levels. These molecules, among other functions, serve an essential purpose of carrying information about which genes to turn on and off. Since they regulate the activity of our genome, scientists wanted to see how they affected sleep during a young age.

They found the concentrations of two miRNA molecules to be different in normal and short sleepers. Even when they took into account participants’ age, sex, pubertal status, country of origin, screen time, and parents’ education levels, it didn’t change the outcome of the results. 

These results could help us create a blood test that would detect these molecules, and objectively asses sleep hygiene in children and adolescents. That could also be useful in preventing many health impairments due to lack of sleep. This objective measurement could prove to be a helpful tool, as relying on self-reporting questionnaires depend on our subjective view.

However, the authors reported a few limitations of their study, such as a weak correlation of sleep duration and miRNA blood levels in the normal sleeping group, and no significant association in short sleepers. Additionally, self-reported questionnaires could be inaccurate, although they are commonly used in sleep assessment studies. Researchers also didn’t include physical activity in the analysis, and this variable could be crucial. 

Generally, sleep duration and quality are affected by many different factors, such as genetics, environment, and others. These findings concerning miRNA concentrations and sleep duration during a young age, even though still weak, could prove to be vital for further research. Of course, more studies are needed to explore the function and importance of these miRNA molecules.


Many people find CPAP machines uncomfortable and stop using them as soon as their sleep apnea starts to feel better. As a result, the disorder symptoms return in full swing, and a recent study highlights this as the main reason for hospital readmissions among OSA patients.

Written by:


, Sleep Researcher
Last Updated: Sun, October 6, 2019
Fact checked by:

Marko Jevtic

, Sleep Specialist

Sleep-related breathing disorders cause partial or complete obstruction of one’s respiratory system during sleep, resulting in many complications such as low blood oxygen, high blood pressure, even heart attack or stroke. The severity of the symptoms varies between the different types of breathing disorders, including obstructive sleep apnea, central and mixed sleep apnea, sleep-related hypoventilation and more. The most common one, the obstructive sleep apnea (OSA) affects about 20% of men and 9% of women in the US alone, which is a big increase comparing to the estimated 3% of the population in the 90s. This is believed to be due to a number of factors, including higher obesity and asthma rates, pollution, but also due to a more precise diagnostic system – polysomnography was discovered and readjusted at the end of the 20th century to monitor respiratory airflow and some other breathing-related functions in our bodies during sleep. To date, it remains the one sure way to diagnose this sleep disorder, also measuring one’s heart rhythm, brain activity, eye movements and so forth.

Several options exist for treating OSA, the most widespread and efficient one involving a CPAP machine. This choice has been proven time and time again as the most effective and remains a go-to option in most circumstances unless it isn’t adhered to for a period long enough to work. Many people find CPAP uncomfortable and stop using it as soon as their OSA starts to feel better. As a result, the disorder symptoms return in full swing, and a recent study highlights this as the main reason for hospital readmissions among OSA patients. Before we get into the study, we will review OSA and CPAP treatments for some context and clarification first.

Obstructive Sleep Apnea (OSA)

OSA is frequently accompanied by loud snoring, interrupted by periods when the airflow is reduced or blocked. This is followed by choking or gasping for air which usually wakes up the person, but only for a brief moment before they resume sleep. Depending on how often this happens, OSA can be:

  • Mild – the episode happens 5-14 times every hour
  • Moderate – the incident occurs 15-30 times every hour
  • Severe – the event occurs over 30 times every hour

Everybody is at a lower or higher risk of developing OSA, depending on some contributing factors such as:

  • Weight. High blood pressure, heart disease, and diabetes are all linked to obesity and known to increase your chance for developing OSA as well.
  • Neck size – over 17 inches for men, and over 16 inches for women increase the risk of OSA.
  • Age. The older you are, the more chances you have at developing OSA, at least until you hit 60. Statistically, the incidence rate drops after that age.
  • Sex. Men are at least two times more likely to develop OSA than women, possibly due to their higher obesity rates and larger neck dimensions.
  • Allergies and asthma both increase the risk because of more sensitive airways, increased mucus production and congestion.
  • Family history. The exact predisposing genetic factor isn’t known yet, but its existence is evident, given that you are more likely to experience OSA if you have a relative who suffers it, too.
  • Retrognathia, meaning that your lower jaw is smaller than the upper one.
  • Narrow airways. These sometimes naturally “happen,” perhaps due to a larger than average tongue or enlarged tonsils.

Treatments usually consist of some lifestyle changes and some specialty therapy with machines like CPAP (more about that in a bit).

Lifestyle changes include:

  • Weight loss – beneficial for everybody whose BMI is outside of the optimal.
  • Switching sleeping positions from back to the side, preferably left, as this aligns the organs and the spine properly while reducing snoring and airway obstruction.
  • Avoiding opioids such as alcohol, pills, cigarettes, etc.
  • Managing secondary conditions if they are present – asthma or allergies, GI issues or another medical condition.
  • Nasal sprays if congestion is what disrupts the breathing.

CPAP therapy

Continuous positive air pressure (CPAP) is a type of PAP treatment most suitable for OSA and some other breathing conditions. It is a machine that is put next to a patient’s bed, connected to a mask they’re supposed to put on at bedtime via a hose. The treatment lasts the entire night. The machine humidifies the air and provides it with high pressure directly into the mask, hence the name. This enables the patient’s airways to remain open, or reduces their obstruction and improves their sleep quality. The duration of this treatment and the specific settings on the CPAP machine depend on the doctor’s prescription based on the severity of your OSA and your overall health. For example, if you have OSA but also some gastrointestinal issue that causes acid reflux, CPAP therapy is not the best option – the air will sometimes stray and pass through the esophagus which is already weak enough, thus exacerbating acid reflux.

Nonadherence to CPAP associated with increased 30-day hospital readmissions

Specialists sought out to discover the effect of nonadherence to CPAP on hospital readmissions expecting to get the general overview of the situation so they conducted this study including 345 patients at the VA Long Beach Medical Center that satisfied the criteria (they were diagnosed with OSA, hospitalized at some point or another from January 2007 to December 2015 and prescribed CPAP therapy). Out of that number, 183 people adhered to their CPAP therapy while 162 didn’t. The purpose of the study was to establish the effect of nonadherence in terms of all-cause, cardiovascular-cause and pulmonary-cause hospital readmissions within thirty days after the initial, index admission discharge from the hospital. Excluded were patients without records of adherence to CPAP therapy and polysomnography to confirm OSA, those who passed away in the hospital during index admission and those transferred to another facility within the same day of index admission.

All-cause readmissions include cardiovascular and pulmonary-cause, as well as other cause readmissions such as renal, urologic, gastrointestinal, neurologic, psychiatric, infection, etc.

Cardiovascular-cause readmissions refer to those of congestive heart failure, coronary syndrome, arrhythmia, peripheral cardiovascular disease, and some others.

Pulmonary-cause readmissions were due to pulmonary hypertension, asthma, hypoxia, obesity hypoventilation, pulmonary embolism, and interstitial lung disease.

The average age of the patients from the adherent group was 66.3 years, and 62.3 in the nonadherent group. This, along with the patients’ sex, BMI, race, environment, and home conditions, the overall state of health and medical history was taken into account before measuring the results. Although the CPAP adherent group was older on average, the expected increase, especially in cardiovascular-cause of readmission, wasn’t apparent. The incidence rate both for all-cause and cardiovascular-cause readmissions was significantly higher in the nonadherent group, and their stay in the hospital was slightly longer, too.


The study confirmed an existing hypothesis that not sticking with your CPAP treatment plan is more likely to get you back into the hospital.

The cardiovascular causes were due to atrial fibrillation (29.0%), myocardial ischemia (22.5%), and congestive heart failure (19.3%), and to no surprise, because these are often the result of frequent apnea episodes and hypoxemia, both of which are neutralized with CPAP therapy.

The pulmonary-related readmissions were also higher among the nonadherent group, but not as much as initially expected, and not of significance to this study.

All-cause readmission unrelated to the two causes mentioned was mostly urologic (10.7%), infection (8.0%), and psychiatric (5.3%). Specialists are just starting to take a closer look into these factors and their association with OSA and sleep in general.

Limitations and critique

Although its significance is notable if only as a single study, this work has faced a couple of flaws from the start and they are worth mentioning for clarification and readjustments for future studies.

For starters, it was conducted in a Veterans Affairs Medical Center, which is a specific target group and not as general as one would hope for a study of this sort. People from this subject group were predominantly white, male, have a lower income, have a history of substance abuse or have a second existing chronic condition. Cause-consequence effect wasn’t completely transparent either, as with most studies. One can’t be sure that CPAP nonadherence was the reason for a future event, only that the event was more likely to happen to people from the nonadherent group, although researchers did include many other contributing factors.

Further, most of the patients who didn’t make the criteria for this study were excluded because of the lack of sleep clinic follow-up within a year after the first hospitalization.  That excludes their results as well, whether they continued the prescribed CPAP therapy or not.

Lastly, because of its small dimensions, the study might have missed some patterns, while some of the patterns noticed could have proved irrelevant on a larger subject group. For this reason, the study remains more a stepping stone for future research, than a sole authoritative source of information.

Some professions can make it possible to balance your monthly income with a healthy, sensible sleep schedule.

Written by:

Tanya Hodgson

, Sleep Researcher
Last Updated: Sun, October 6, 2019
Fact checked by:

Marko Jevtic

, Sleep Specialist

If you ask any hard-working adult you can find, chances are high that you’ll hear complaints about how little they sleep. The idea that you can either make a lot of money or sleep well (and not both) is widespread enough to be considered an ingrained part of our common knowledge. Stories of incredibly busy executives, writers, and shift workers hover in casual conversations, convincing people that sleep is something you have to sacrifice in order to make enough money to live comfortably. Due to how finances play into our daily life, most people prioritize money over sleep if they feel like they have to choose only one.

But do they? There may be professions you can aim for if you want to balance your monthly income with a healthy, sensible sleep schedule. This article aims to explore just that and provide info on where you can get a job that allows you to get enough rest to avoid illness and fatigue. We will look at various fields and use the American Time Use Survey (ATUS, published by the Bureau of Labor Statistics) to determine who gets paid the most and who sleeps the most. The idea that career success often has to come at the cost of the person’s health doesn’t hold as much water as some people claim, fortunately. However, there is some truth in such claims. Let’s get into it.


What Was Our Methodology?

We were mainly concerned with US residents and their average income and amount of time spent asleep per night (on average). In order to get reliable information, we looked towards the ATUS. This survey was conducted with 10,000 respondents, and the information they willingly revealed about their monthly income, sleep, and other factors. This data was contained within three separate yet connected ATUS resources, each of which was designed to collect specific types of information from the respondents. The sources we consulted were:

  • The ATUS Respondent data file, which was created to store information about the wage and employment status of each respondent. This file is where we pulled income numbers from to get our results.
  • The ATUS Activity Summary data file, which contains detailed information on the sleeping habits of every respondent. As the purpose of this article is to measure how much sleep common professions “allow,” this file played an instrumental role in our research.
  • The ATUS Roster data file, containing basic information provided by the respondents, including age, gender, etc. While this information played a somewhat lesser role in our overall assessment, it helped paint a clearer picture as to who’s the most susceptible to sleep deprivation.

Getting the data is only the first step. With this information “in hand,” we could start our analysis. The second step was to reduce the number of entries only to those that would fit our criteria. It means we were forced to remove entries where the respondent did not provide necessary information about their wage and work schedule (meaning their precise work hours, more or less). This filter alone reduced the number of entries to around 3,150, but we were not finished. It was important to establish a strict set of criteria, which meant the removal of entries where subjective interpretations caused skewed responses when it came to employment status (where the respondents would give vague or non-specific answers due to working as contractors or working part-time). At the end of our filtration and limitation process, we were left with a rough figure of 1500 respondents. While it’s hard to assume that our numbers mirror the population at large, we consider it a suitable enough sample size to make the estimate we needed to make.


The Results

The ultimate goal was to compare professions based on how much money they generate and how much sleep they tend to allow (or “take away”). The results were mixed in the sense that some of the estimates follow what you might hear in casual conversations among non-specialists, whereas others deviated further from our original expectations from when we began this process. As a whole, we’ve discovered that there is a considerable amount of truth behind the idea that good salaries often “necessitate” bad sleeping habits, not every profession fits into this mold. We will list a good amount of professions to paint a clear picture as to where you should seek employment if you value your sleeping hours (which you should, for the sake of your health and the safety of those around you).

For example, it shouldn’t surprise you that lawyers and other legal specialists generate some of the highest salaries (often earning around $1850 over the course of a 42-hour work week on average). However, this comes at a cost – with legal specialists being closer to the lower extreme of hours spent asleep (with an average of 7.2 hours per day, but frequent situations where they get less than 6 hours in a given night). Legal cases impose a lot of stress on the worker and often demand extra hours of effort, which can all add up to a very unstable sleeping schedule and frequent scenarios where the person is functioning on a small amount of sleep. Additionally, there is a large pay gap between the lower and higher ends of the legal hierarchy, to the point where paralegal specialists and people in similar positions often don’t make enough money to justify the hit to their sleep schedules.  

One of the worst possible places to be in your career is the position of a healthcare assistant or medical aide. These jobs are demanding and stressful, creating a problem where it’s very hard to hit the recommended value of 8 hours of sleep per night, especially since shift work is often involved (we will talk about this separately, later on in the article). In the worst case scenario, a person in this position may expect to go to work with less than 6 hours of rest the previous night. The reward for this level of effort is nothing to brag about either – healthcare assistants and aides make an average of $426 per week, which is definitely one of the lowest figures we’ve noticed.

If you’re looking for good rest but aren’t bothered by a low salary (for whatever reason), you want to look towards food service or personal care industries. Bartenders, hairdressers, and waiters average in at close to 9 hours of sleep per night on average, which is more than enough to keep you healthy and energized. However, these positions often come with some of the worst salaries you can find, with an average value of around $400 or slightly less.

Working in the art industry can mean many things, but in this case, we will focus on graphic designers, fine art, film editing, and 3d model work. You most likely won’t find an optimal amount of sleep in these fields. The average amount of hours spent sleeping per night hovers at around 7, with situations where you have to sleep for roughly 5.5 hours on some days. However, the pay isn’t bad at all – work schedules that demand only around 32 hours of work each week can result in salaries of $1050. If you’re really lucky (or simply amazing at your job), you could see salaries that approach $1700-1800, which makes jobs like graphic design incredibly appealing.

One of the most rewarding professions when it comes to both monthly income and sleep economy is coding. Programmers and math scientists regularly clock in almost 8 hours of sleep per night, which lets them focus on their work that much more effectively. This increase in efficiency may have something to do with their earnings – programmers usually work around 50 hours per week (at worst), but they rake in almost as much money as lawyers (who have to work a lot more) – around $1750 per month on average. If you’re trying to choose something to study, coding may be the way to go, as it is always in demand (and seems to be accelerating due to the exponential growth of technology in the modern age). You get to sleep a lot and also improve your life using a chunky salary.


Workplace Risks and Sleep

While it’s safe to consider any job unhealthy for your sleep if it offers you less than 7 hours of sleep per night on average, there are other, less obvious problems to consider. Fatigue (often called excessive daytime sleepiness) is the most common result of any sleeping problem (including sleep disorders), and it causes the person in question to become way less efficient at virtually anything they do. Your perception gets considerably worse, and you start to miss things you would notice on more hours of sleep. You become more prone to taking risks, and your memory, hand-eye coordination, and similar things take a massive drop in quality.

As a result of all this, workplace accidents become more likely when you’re involved, if you have fatigue. Some job positions put you at more risk simply through what you have to do to perform your job. We’ll use transportation jobs as an example – both drivers and pilots are put in potentially extreme danger if they’re sleep-deprived. They endanger not only themselves but also their passengers and anyone in the immediate area. Driving jobs often don’t limit your ability to get proper rest, but they’re the worst possible thing you could be doing if you’re heavily fatigued. Drivers sadly also make poor salaries.

Keep in mind that any kind of job that involves mandatory shift work is practically guaranteed to ruin your sleep schedule and cause lots of fatigue, even if it pays well. Sometimes the hours spent working don’t mean everything, as the nature of the job could expose you to health risks or direct physical danger. Know what you’re getting into when applying for work – a person with an established sleep disorder should not work in positions that require precision or good reflexes, for example.


According to research, most animals sleep in some form, including fish.

Written by:


, Sleep Researcher
Last Updated: Sun, October 6, 2019
Fact checked by:

Marko Jevtic

, Sleep Specialist

Research has shown that most animals do sleep in some form. While REM sleep and dreaming might only be reserved for mammals and birds, all other animals also require some rest. Even jellyfish, one of the oldest known multicellular organism, with the most simple nervous system, has been observed to experience some form of sleep. They have been around for more than 500 million years, long before the dinosaurs even existed. Because of this discovery, it is proposed that sleep is widespread among all of the animal kingdom, and it serves a crucial purpose of restoring body and mind, as well as forming memory and learning.

When we think about how sleep works, we often imagine laying down in a comfortable position in our bed, with our eyes closed, disconnected from the world. Because of that image, people often have a hard time imagining if animals can sleep. It’s easy for mammals, as we’ve seen tons of cute sleeping dog and cat videos, but when it comes to animals that we are less familiar with, we don’t have a clue. If your kid has asked you if their pet goldfish sleeps, and you didn’t know what to say, don’t worry, we have all of the answers for you.


How Do Fish Sleep?

Fishes do not have eyelids, so they can’t close them. One of the purposes of eyelids beside protecting an eye is to spread the fluid across it, so it can function adequately without drying out. When you are always in the water, you don’t have that problem. Fishes also have a far simpler central nervous system than mammals, so they don’t have specific regions of the brain that we do. Take neocortex, for example, that plays a considerable role in sleep. It is a part that produces certain brain waves that are distinctive in different stages of sleep in humans. Also, it is very active while we are dreaming in REM sleep, which means that fish don’t experience REM sleep and that they most likely don’t dream. We say most likely because we can’t be a hundred percent certain, considering how complicated even the fishes’ central nervous system is. Future scientific research might show that they, in fact, experience dreams, but that the other parts of the brain are involved.

Because fish are lacking these structures that would undoubtedly say that they are sleeping, we had to define other parameters to describe the way they rest. These are:

  • A state of prolonged inactivity
  • A typical resting posture
  • The repetitive pattern of this inactive behavior during the 24-hour cycles
  • Reduced perception of external stimuli

According to these criteria, sleep in fish is a period of inactivity, almost always with the same posture and in the same location, at the same time every day, while having decreased sensitivity to outside disturbances. Another criterion might be the presence of “rebound sleep.” The induced absence of sleep-like behavior for some time should mean that the inactivity will be more present during the following days that fish is left alone.


The Difference in Sleep Habits Between Fishes

There are over 30,000 species of fish, so naturally, there is a lot of variation in the way that they sleep. Sometimes, even those four parameters that we have described are not enough to tell if the fish is sleeping or not, cause they might not fulfill all four, but it is apparent that they are resting.

Some quietly float on the surface or near the bottom, while others drift round with an occasional flick of a fin to keep them going. Some get the needed rest under a rock, in a whole, or in hiding between marine algae. There are some that even create nest-like structures in the sand and the ones that bury themselves when going to sleep. Some parrotfish have glands inside the gills that secrete mucus. This way, when going to sleep, they produce a cocoon, that protects them from parasites, but it also blocks their smell from potential predators lurking nearby.

Some species like green bromis sleep in branching corals, and they have evolved an interesting symbiotic relationship. While fish is sleeping, it energetically moves its fins, increasing the flow of oxygenated water around the corals. Because algae that live there can’t photosynthesize and produce oxygen during the night, it looks this peculiar sleep behavior is needed for the coral survival.

Spotted wolfish is a beautiful example of how fish behavior can be similar to our sleep. Because it doesn’t have pelvic fins to stabilize its body, this fish flips on its side while sleeping. Others, like bluehead wrasse, are so unresponsive during the resting period, that scientist stated that they were even able to pick them up by hand and bring them to surface without waking them up.

Some fish even catch some rest while schooling. There are a lot of fish in the school that can spot the predator if it comes nearby, so some members decide to turn on autopilot and snooze for a bit. Another fascinating thing about fish is that they can produce electrical waves and communicate by them, so electrical signal can fastly spread between school and alarm everybody about the danger.

As the quality and quantity of light can vary drastically with the depth of the water, other factors can tell fish when is the time to rest. The temperature of water, availability of food, and the presence of predators are all valid signals for a fish for adjusting their sleep/wake rhythm. Some even can switch between sleeping at night or day, depending on these other factors.

The most studied fish is zebrafish (Danio rerio). It’s a great model organism as it shows clear signs of sleep, it stops moving, it’s breathing and heart rate slow down, and it takes much longer to respond to outside stimuli. It’s also observed to get a rebound effect, meaning that when deprived of sleep for some time by the researches, it tries to catch up on the lost sleep when it is left alone in the dark again. However, if the light stayed on, the rebound effect has not been observed. The study of zebrafish is providing some good info about how sleep works, and how the sleep deprivation can affect animals as well.


Do All Fish Sleep?

Most fish are diurnal animals, meaning that they are active during the day and sleep at night. However, there are some that are nocturnal, so they are active during the night and resting during the day. Weirdly, there are some fish that seem not to sleep at all.

Bluefish and mackerel continuously swim in the big seawater aquaria, and even though they seem to slow down at night, they remain responsive to outside disturbances and the introduction of food. However, scientists argue that this state is induced due to the high stress of living in captivity.

There are some fish that have a prolonged period of sleep absence, or they seem to be completely lacking the rest:

  • Tuna and some sharks seem not to sleep at all. Scientists are still not sure why that is, but they hypothesize that it is because of the role that sleep has on memory and storing information. Rest serves a purpose to embed memories in our brain and to process all the stimuli that we get during the day. Since those fishes sleep in a rather boring environment, in the deep ocean where the scenery doesn’t change much, it is suggested that they don’t need to relax. Some cave-dwelling fish are also restless, and it may be for the same reason, lack of visual sensory input. However, some scientists are not sure that these creatures are entirely sleepless, and they attribute it to a lack of observation. They propose that some sharks and tunas might have bursts of microsleep, that are observed in some other animals.
  • Some fish lack sleep during the juvenile stage. Mozambique tilapia is one of those, and it is observed that it doesn’t sleep for the first 22 weeks of its life. Since tracking rest patterns for a long time in fish is not the most attractive topic of research, scientists still need to figure out whether this is a common phenomenon. Larvae and adults of zebrafish seem to follow the same sleep patterns.
  • No rest during migration. Fish seem to be occupied during the period of movement, so there is no time to catch some snooze time. It’s interesting that scientists have created an experiment where they simulated the autumn condition during the winter to see how the tautog would behave. They usually migrate during the fall, so they started to be more active and didn’t sleep. The juveniles weren’t affected which is consistent since they don’t migrate; only adults do.
  • Lack of sleep during spawning or parenting period. Some species like the mentioned tautog, bullhead, minnows, yellow perch, and many others seem to be active continuously through spawning season. Others do that when it’s time to care for their eggs. Because eggs need the flow of oxygen all the time, fish look after them and fan them to provide a continuous stream of oxygenated water.


Why Do Fish Sleep?

It seems that this resting period in fish has the same crucial restorative function as it does in humans. Sleep is a time when our brain can do a little maintenance, and it can send signals to repair muscles and other tissues in our body. It’s also a period necessary for our memory storage and learning, and it seems that it plays the same role in fish as well. It’s just that their brains are much simpler than ours, so the effects are not as apparent. Because of the simplicity of their central nervous system, they also don’t go through the same sleep stages as we do, and they don’t experience REM sleep and don’t seem to dream.

Fish can also switch the time of the day when they sleep depending on the outside conditions. Water temperature, the presence of predators, and availability of food can trigger this. Atlantic salmon is an example of this, as they turn nocturnal in colder waters. Fish are not endothermic organisms, like mammals and birds, and their body temperature depends on the temperature of water. Their muscles also produce heat while swimming, so they have to keep move to be warm. Some fish like tuna produce so much heat that they are considered partially endothermic. When the salmon gets in the colder waters, they slow it down (as they turn a bit sluggish) so being active during the night provides them some safety against predators.


Sleeping Goldfish

Another valid question about our pets, since they are not in the wild is how they sleep in a tank. And do our pets like goldfish, guppies, and betta fish sleep at all?

Guppies like sleeping in the dark, so they mostly rest at night when all the lights are off. They usually hover in one place just above the bottom. Sometimes they can float on the surface, but if this happens during the day, it is an indication of some problem.

Bettas sleep in a variety of ways, some float in one place, while others can rest on a substrate or plants in their aquarium. Their gill movement is considerably lower during this period.

Goldfish are diurnal, meaning that they are active during the day. They’ll most likely sleep at night when you turn all your lights out. These pets are low maintenance, and despite the popular belief, they are quite smart. Forget about that myth that they only have a few second memory span; they can remember things for months, even a year. They can also be trained to respond to different kind of music, color, or other sensory cues. In one interesting experiment, scientists thought goldfish to press a lever to get food. Then they limited the time during the day when they would get food by pressing a bar to one hour. It took them very little to learn this, and not only did they use this opportunity to get extra food, but they also didn’t touch the leaver during the hours that it didn’t have a rewarding effect, meaning that they very much have a developed memory and a sense of time.

If your fish is sleeping upside down or on its side, know that this isn’t a usual behavior, unless they told you that it is how that species rests. Other than that, it most likely indicates a health problem, and you should take your pet to the vet.