Too Little Sleep Harms Cognition. So Does Too Much.

Too Little Sleep Harms Cognition — and So Does Too MuchIn recent years there is a growing amount of evidence showing a direct negative impact between diminished sleep and a variety of complaints, including cognitive function.

Recently researchers from Western University’s Brain and Mind Institute in Canada set up the largest sleep study ever conducted, examining data from 40,000 people. Dr. Adrian Owen, a cognitive neuroscience researcher at the Western University Institute explained, “We really wanted to capture the sleeping habits of people around the entire globe. Obviously, there have been many smaller sleep studies of people in laboratories, but we wanted to find out what sleep is like in the real world.”

The large number and extreme diversity of the participants in the Western University Institute study allowed them to compare the impact of varying amounts of sleep on people in a highly diverse age range, a large variety of professions, and from many different backgrounds.

Their preliminary findings, based on a careful analysis of 10,000 of the participants, was recently published in the journal Sleep. Although this report represents data from only one-quarter of the participants involved in the study, it will take quite some time before all the data can be analyzed carefully. Nevertheless, the information derived from the analysis of 10,000 of the participants allowed for statistically significant conclusions to be drawn.

An extensive questionnaire was used to collect background information. Not only were questions of age, education level, and the location included, but even more detailed information, such as which medications participants took, was requested, as well as information about any other factors that might contribute to the quality and quantity of sleep.

The volunteers underwent a series of 12 well-established cognitive tests in order to correlate the amount of sleep with their cognitive ability. When all was said and done, some of the results reported reinforced previous research about sleep.

Many of us can remember being told since the time we were children that it is important to get 7 or 8 hours of sleep each night. So it was not surprising that people who got 7 or 8 hours of sleep each night had with the highest level of cognitive functioning. This was true across age groups, locations, levels of education, and other factors.

It was also noted that the greater the sleep deficit (defined as length of sleep less than 7 hours), correlated directly with a decline in cognitive ability. Further, since sleep problems among the elderly are extremely common, both in quality and duration, deprivation of sleep among the elderly was linked with a large decrease in their cognitive abilities.

The authors of the study stated,” These findings have significant real-world implications, because many people, including those in positions of responsibility, operate on very little sleep, and may suffer from impaired reasoning, problem-solving, and communication skills on a daily basis.”

Other results, however, were quite surprising. One such finding was that both too little and too much sleep impacted cognitive abilities. The study showed that those who slept too much had a similar level of cognitive impairment as those who slept too little.

Individuals who slept four hours or less per night displayed a cognitive level of someone 8 years older than people the same age who slept 7 to 8 hours each night. However, those who slept 12 hours or more each night also tested at 8 years older than their biological age.

It should be noted that people without physical illness who are sleeping 12 hours or more each day may be suffering from depression or other mental or physical illness. It is unclear whether this is the reason that people who slept more than the optimum 7 to 8 hours per night performed poorly on cognitive tests, or whether the extra sleep itself caused the poor performance.

The bottom line for us is to remember that a regular, healthy schedule is always in our best interest. Whether it’s eating habits, exercise habits, the time we get up and go to sleep each day, building healthy habits will help us to feel better, perform better — and even to think better.

At Atlantic Coast Healthcare and Rehabilitation Center, in Lakewood, NJ, we pay close attention to the needs of our residents, including the amount of sleep they get.

Read our reviews on,, and to hear what our residents and their families have to say.

Or better yet, come see for yourself: Contact us to schedule a tour by calling 732-364-7100, or by clicking here.

Leave a Comment