Short Sleepers and Daytime Dysfunction

A new study out of the University of Utah published in Brain and Behavior has noted that there are neural connection patterns in the brains of short sleepers that suggest some of them may actually be getting enough sleep, but may also be more tired than they realize.

Habitual short sleepers are those who can sleep far less than the recommended amount without experiencing any daytime symptoms.

Dr. Jeff Anderson, co-author of the study, noted that the evidence helps them understand why some people do not seem to need much sleep.  He suggested that it is possible some brains can actually do the “restorations” done in sleep throughout the day while awake.

Sleep is one of the most essential functions of our body, though researchers are still unable to say exactly why that is, which makes it such an active field of research.

For the most part, scientists believe that sleep helps clear the brain of clutter thoughts that have accumulated throughout the day, and it allows for essential pieces of information to be stored in short or long-term memory centers.

Most people who get less than 7-9 hours of sleep have daytime symptoms like irritability, fatigue, and inability to concentrate.  There are a host of physical and mental health problems associated with chronic short sleep durations, including heart disease, mood disturbance, obesity, decline in cognition, and increased mortality risk.  This is not to mention the increased risk of accidents due to tiredness.

Interestingly, some can sleep six or less hours a night and report no ill effects.  In a study done in 2009, University of Utah neurologist, Chris Jones, along with his colleagues, found genetic mutations associated with short sleep duration.  The genetic factors found in this study suggest that those who can function properly on six hours or less of sleep may feel fine, but actually have “tiredness” in the mind and organs.

To answer the questions about how short sleepers can function without side effects, researchers looked at brain wire mapping.  Their goal was to figure out the connections of neurons underneath the sheath of brain cells.  The idea was to figure out how the connections are related to functionality with and without sleep.

The Human Connectome Project is a multi-university consortium that is analyzing these brain connections in 1200 people.  They are using MRI scans.  So far, data for 900 patients have been released, which allowed the University of Utah researchers to analyze the brain connectivity.

The data was split into two groups: Those who reported normal sleep duration and those who reported six hours or less a night over the last month.  The short sleepers were divided again into two groups:  Those who had daytime symptoms and those who did not.

Both short sleeper groups had connectivity patterns on MRI that were more associated to sleep than wakefulness.  People were instructed to stay awake while in the MRI; however, Dr. Anderson noted that short sleepers often drifted off while lying there in the scanner.  That includes even the people who reported no daytime dysfunction.

One hypothesis about short sleepers who deny daytime dysfunction is that their awake brain systems are in overdrive.  This suggests that while lying still and bored in an MRI scanner, they had nothing else to do than fall asleep.  There are several public safety implications in this hypothesis, because there are other “boring” activities like driving and operating a machine by rote memory that could lead to injury or accident.

Short sleepers who denied dysfunction showed increased connectivity between the cortexes that process sensory information and the hippocampus, which is responsible for memory.  Those short sleepers who fell asleep in the MRI scanner may have been performing memory consolidation, which is not something non-short sleepers can do.  This is indicative of short sleepers being able to do memory consolidation that is usually done during sleep while they are awake, reducing their need for sleep.  They could also be falling asleep during the day without even realizing it.

As with all new findings, further research is necessary to test the hypothesis.  The next part of the research that the University of Utah team will focus on is whether short sleepers without daytime dysfunction are actually doing well clinically.

In the next study, researchers will find people who sleep six hours or less naturally, regardless of the day or whether they are on vacation.  They will perform brain imaging and examine cognitive performance like driving simulator testing, which will give them objective information about how they are truly performing.

Insufficient sleep may also be affecting their ability to perceive any daytime dysfunction.  The research team is particularly interested in understanding the perceived symptoms or lack thereof in short sleepers.

The analysis of the connectome data showed the team in Utah that self-reporting sleep duration played a role in the variation between resting connectivity profiles.  Further functional MRI studies should take that and the actual sleep duration into account while interpreting results.

The researchers are hopeful that this ongoing research will answer the key questions about why each person needs a different amount of sleep.


Rachael Herman is a professional writer with an extensive background in medical writing, research, and language development. Her hobbies include hiking in the Rockies, cooking, and reading.

Rachael Herman

Author: Rachael Herman is a professional writer with an extensive background in medical writing, research, and language development. Her hobbies include hiking in the Rockies, fishing, and reading.
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One Reply to “Short Sleepers and Daytime Dysfunction”

  1. Eileen Glynn

    I have been a life long insomniac short sleeper and most of the time I have been able to function well. I attended college, taught, exercised, raised a family and carried on normal daily activities, many requiring a lot of cognitive demands and concentration. I am now using an APAP machine for a year and a half and rarely nap. I am still sleeping only 5 to 6 hours a night. I have been retired for a year and rarely use an alarm clock. The machine records how long I have the machine on and I rarely sleep longer than 5 or 6 hours, sometimes less than 5 hours. I try to sleep longer but I just can’t.

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