HEALTH & WELLBEING

Studies have found that not getting enough sleep makes it more likely to catch the common cold or flu. In a viral exposure study, compared to sleeping more than 7 hours per night, people who slept less than 5 hours had 4.5 times greater risk of developing a cold, while those sleeping 5–6 hours had 4.24 times greater risk.

Key study: 

Behaviorally Assessed Sleep and Susceptibility to the Common Cold | PMC

Lack of sleep can cut learning ability by up to 40%, and sleep before learning helps prepare the brain for memory formation. Studies using targeted memory reactivation (reminding people of something they learned while they slept), found that people remembered things 13% to 53% better than when no reminders were used, which is about 36% better on average.

Napping has been shown to improve performance on perceptual learning tasks, activities where people learn to notice small differences in what they see. During these tasks, naps lower discrimination thresholds, meaning people can tell things apart more easily and accurately after sleeping.

Key studies:

How Snoozing Strengthens Memories | NIH News in Health

Electrophysiological markers of memory consolidation in the human brain when memories are reactivated during sleep | PMC

Sleep after learning aids the consolidation of factual knowledge, but not relearning | SLEEP | Oxford Academic

The impact of frequent napping and nap practice on sleep-dependent memory in humans | Scientific Reports

Drivers missing 2–3 hours of sleep in a 24-hour period are over four times more likely to crash than drivers who get 7 hours. Drivers who slept 1 or more hours less than their usual amount had significantly higher crash rates, with those sleeping 4+ hours less than usual having 10.2 times the crash rate. Sleep-deprived employees are 70% more likely to be involved in workplace accidents than well-rested colleagues.

Key studies: 

Missing 1-2 Hours of Sleep Doubles Crash Risk | AAA Foundation for Traffic Safety

Acute Sleep Deprivation and Risk of Motor Vehicle Crash Involvement | AAA Foundation for Traffic Safety

Sleep Disorders and Sleep Deprivation: An Unmet Public Health Problem

Losing just one night of sleep makes the brain’s emotion center (the amygdala,) about 60% more reactive to negative pictures. It also becomes less connected to the pre-frontal cortex, the part of the brain that helps control and calm emotions.

A meta-analysis of 64 studies found sleep loss resulted in a moderate positive effect on negative mood and a large negative effect on positive mood. Researchers have found that participants who were limited to 4.5 hours of sleep for one week reported feeling more stressed, angry, sad, and mentally exhausted.

Key studies: 

The Role of Sleep in Emotional Brain Function | PMC

The effect of sleep deprivation and restriction on mood, emotion, and emotion regulation: three meta-analyses in one | PMC

Sleep and Mood | Sleep Medicine

Multiple large meta-analyses show that sleeping 7–9 hours per night is linked to a low mortality risk. A meta-analysis of 16 studies with 1.3 million people found that sleeping less than 6 hours increases the risk of death by 12%. Both too little and too much sleep are linked to health problems affecting metabolism, hormones, and the immune system.

People with all five favorable sleep behaviors were 30% less likely to die for any reason, 21% less likely to die from cardiovascular disease, and 19% less likely to die from cancer. Sleep deprivation leads to rises in blood pressure, increased insulin resistance and diabetes risk, accumulation of belly fat, and prevents the brain from flushing away toxic byproducts.

Key studies:

Sleep Duration and All-Cause Mortality: A Systematic Review and Meta-Analysis of Prospective Studies | PMC

Getting Good Sleep Could Add Years to Your Life | American College of Cardiology

Sleep and longevity: How quality sleep impacts your life span | Mayo Clinic Press

Sleep regularity is a stronger predictor of mortality risk than sleep duration: A prospective cohort study | SLEEP | Oxford Academic

A study showed that being awake for 17 hours makes the brain as impaired as a 0.05% blood alcohol level, and being awake for 24 hours is like having 0.10%, which is above the U.S. legal driving limit. After 17–19 hours without sleep, response speeds were up to 50% slower.

In a study, sleeping only 6 hours per night for two weeks caused thinking and memory problems similar to staying awake for an entire night.

Key studies:

Moderate sleep deprivation produces impairments in cognitive and motor performance equivalent to legally prescribed levels of alcohol intoxication | PMC

Neurocognitive Consequences of Sleep Deprivation | PMC

Two nights of sleep deprivation significantly decreased motivation and vigor, while significantly increasing feelings of fatigue. Sleep restriction, three consecutive nights with 3-hour sleep opportunities, reduced the willingness to exert cognitive effort in healthy young adults compared to when fully rested

Sleep-deprived study participants felt that workload increased, walked slower, completed tasks more slowly, worked less efficiently, and tried fewer solutions. When sleep-deprived, cognitive performance is experienced as more effortful, and motivation to perform tasks decreases.

Despite participants of one study trying to compensate with increased effort, they still experienced decreases in both subjective and objective performance and decreased positive affect. Another study shows that sleep extension (increasing the amount of time slept,)  showed marked improvements in vigor and significant decreases in fatigue.

Key studies:

Effects of two nights of sleep deprivation on executive function and central and peripheral fatigue during maximal voluntary contraction lasting 60s | ScienceDirect

Sleep Restriction Reduces Cognitive but Not Physical Motivation | PMC

The effects of sleep loss on capacity and effort | PMC

Sleep deprivation, effort allocation and performance | ScienceDirect

Mild to moderate partial sleep deprivation is associated with increased impulsivity and decreased positive affect in young adults | SLEEP | Oxford Academic

The Effects of Sleep Extension on the Athletic Performance of Collegiate Basketball Players | PMC