Can We Measure Sleepiness and Sleep Deficiency?

Is not the color and the size of our under-eye circles enough to tell just how much sleep-deprived are we? How do we measure sleepiness or sleep deficiency? Read on to find out!

Is not the color and the size of our under-eye circles enough to tell just how much sleep-deprived are we? Or the fluttering of our eyelids is not too obvious? How do we measure sleepiness or sleep deficiency, when they are not even physical things and represent very individual feelings and conditions? For example, two persons can sleep for 8 hours straight, but one will get sleepy sooner than the other one.

Since scientists started paying so much attention to sleep, more and more sleep mysteries began showing up and finding a way to measure what seems unmeasurable appears to be one of them. In today’s post, we are going to see what is considered for these two conditions and in which ways are researchers trying to find out how to measure sleepiness and sleep deficiency.

Sleep Deficiency

Sleep deficiency is considered to be the same as sleep deprivation, which is not a mistake, but sleep deficiency is a somewhat broader term which covers consequences of the lack of sleep (sleep deprivation), poor sleep quality caused by some sleep disorder or sleep-wake phase disorders.

Since it is widely known that people in the US are not getting enough sleep, sleep deficiency has become a common health problem for people of all ages and gender. It has been estimated that around 7% to 19% of people are not getting enough sleep time each day, 40% of adults have fallen asleep during the day without intention at least once in a month. And, another worrying fact is that 50 to 70 millions of Americans are having some type of a chronic sleep disorder. Clearly, sleep hygiene has been very neglected among people in the US.

But, sleep deficiency is not a standalone problem, since it usually triggers other health-related issues such as diabetes, high blood pressure, kidney problems, obesity or depression. It also interferes with our daily chores, job, school, social life, driving, etc. It can cause problems with memory, stress, learning, focusing, and it will also mess up your emotions, mood, and judgmental abilities. So clearly it is not as naive as it may seem at first. It is a myth that sleeping is overrated because it is actually underrated.


We all feel sleepy once we start approaching our bedtime, we begin to yawn, our eyelids are fluttering, and our mind is halfway to the dreamland already. And that is a healthy, usual way of feeling sleepy, but sleep-deprived people are experiencing a much harder type of fatigue and sleepiness called excessive daytime sleepiness, which usually tends to become chronic. Although sleepiness occurs as a consequence, at the same time it is also a cause of many other issues that can appear such as mood swings, stress, and depression.

The problem is that many Americans are willfully limiting their sleep time, which sounds ridiculous at first, but when you think about it, people are under constant pressure of working hard and providing for them and their families, and as a consequence, they are constantly sleep-deprived, and the primary symptom of it is sleepiness. Some other causes of acute or chronic sleepiness can be jet lag, working in shifts, or simply skipping a night of sleep in order to catch up with work or exams.

Sleepiness is just like sleep debt hanging around our neck, and once you get it, it seems impossible to get rid of it since it is hindering our daily life, it affects our ability to focus, work or think clearly. Sleepiness is especially dangerous for drivers since it can be so easy to fall asleep behind the wheel, and drowsy driving has been recognized as responsible for more than 100.000 collisions on the road each year.

Some people try dealing with sleepiness by drinking too much coffee during the day, but that just closes them in an enchanted circle. Coffee will keep you awake, but it will also probably postpone your desired bedtime, causing you to go to sleep later even though you have to wake up in the morning, you will not feel rested, and you will already be sleepy once you wake up. There is no such thing as a cure for sleepiness, in order to get rid of it you have to solve the primary problem which caused it. Many sleep disorders can mess up our sleep routine and then cause excessive daytime sleepiness, restless leg syndrome, sleep apnea, narcolepsy, insomnia, are just the most common ones.

How Can We Measure It?

Well, as we mentioned previously, it can be hard to determine the level of sleep deficiency, and sleepiness since both categories are highly individual and depend on many different factors. So although there are some ways which can nearly determine the current state, it can never be precisely estimated as it can change in a few minutes.

    • Reaction time – this is one way of attempting to measure sleepiness and alertness, but it is still not the best one since the final results can be hindered by many things like medications or brain injuries, so this method cannot really be adjusted to all the specific circumstances and thus it is not objective enough. In diagnosing sleep disorders or mental health problems, various tests are often incorporated, and one of them is the test of vigilance and physical performance. The psychomotor vigilance test lasts briefly, less than 3 minutes, it is designed and created as a simple interactive video game, and it requires quick responses, so it is able to provide us valuable information about the reaction time and overall alertness. Despite the fact that this test is quite accurate and current, there are no indications or information about the way how the individual will perform in a future state of sleep deprivation. Researchers are trying to see whether or not the people with excellent quick results from psychomotor vigilance tests perform better or worse than others when they are sleep deprived, do age or gender play any role? So far there has been no correlation between these characteristics, but many things are still opened and unexamined.
    • Biomarkers – If we could have a generally reliable marker for sleepiness and sleep deficiency, it would be much easier to determine their level. That will be particularly beneficial for some professions that require wakefulness and full attention like airplane pilots, doctors or drivers. The search for biomarkers is essential as they could indicate necessity, history, and future disorders in sleep. Many different neurochemicals and biochemicals are involved in circadian rhythms, so it is possible that a combination of some of them could be the ideal biomarker that researchers are looking for. Various biological indicators and neurochemical have been connected to different aspects of sleep, but each one of them also has another function which is not sleep-related; therefore they are not as specific as they should be in order to be considered as biomarkers. The ideal biomarker would guide us to a particular change in some physiological function connected to sleep. Which is exactly what reaction time tests lack, they are not specific enough, but for now, different forms of these reaction tests are the best we have. Perhaps combining data from all variations of this test could be more helpful in the process of understanding another one of sleep mysteries.
    • A scale – researcher from Australia, dr Murray Johns, established an Epworth Sleepiness Scale for children and adolescents during the 90s, in the form of a short questionnaire with scaled answers, but it is not meant to be used as a diagnostic tool on itself. It consists of 8 questions with a 4-point scale for answers. The score ranges from 0 to 24, the higher the score, the higher are the chances that the person will be dealing with daytime sleepiness in the future. It takes only 2 or 3 minutes to fill it up, and it is available in many world languages.
    • Genetics – this can also be the key solution for measurement, scientists have detected a gene which can be responsible for the fact that some people are more liable to sleep deprivation while others are dealing better with it, but no tests have been taken to examine it thoroughly enough.
    • MSLT multiple sleep latency test is performed in sleep clinics as a reliable way of collecting data about patients sleep habits. It’s particularly used to measure daytime sleepiness, and how quickly a person falls asleep. During this daytime sleep study, patients will have to take five scheduled naps, with 20-minute breaks in between. Even though it is daytime, patients will be in dark and quiet lab rooms, while sensors are monitoring whether the patients are sleeping and in which sleep phase are they.
    • Blood test – this way of detecting sleep deficiency has recently been tested by the sleep researchers in the United Kingdom, and it is still in the process of improvement. Their study was trying to develop a blood test that will target the biomarkers of sleep deprivation. They kept 36 participants awake for 40 hours, during which they were taking their blood samples multiple times. Later they analyzed changes in sets of genes by a machine learning algorithm, and they were able to detect 68 genes which were affected by the sleep deficiency. Also, they managed precisely to find out, with 92% of accuracy, which blood samples belonged to sleep-deprived participants, and which ones were from those who were well rested. They showed that lack of sleep has an impact even on our blood, and paved the path to many other types of blood-related researches.
    • MWT – the maintenance of wakefulness test is.used to measure alertness and if the patient is able to stay awake for a scheduled period of time. So contrary to most sleep studies, such as MSLT or polysomnogram, this one does not have a goal to put patients to sleep but to keep them awake. Patients are asked to sit still for 4 or 5 trials that last 40 minutes. They should look forward and avoid any action that can stimulate their wakefulness. During that time, they are wired to monitors which follow their eye and chin movements, and also their heart and brain activity. Between each trial they have 2 hours of break time during which they can watch tv, read a book, eat or walk around the clinic, the only thing that they cannot do is to go outside and expose themselves to daylight. Patients who do not have a severe problem with daytime sleepiness should not have issues with staying awake up to 40 minutes. If a patient falls asleep, the trial is stopped before the 40 minutes expire, and after a total of 4 or 5 trials, sleep doctors will analyze collected data and set a diagnose.





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