The potential short-term impacts of sleep on cognitive performance are wide-ranging.

Most people are familiar with the daytime effects that result from a night of poor sleep, such as drowsiness and fatigue. In response, a person may inadvertently nod off for a few seconds, which is known as a microsleep.

While a night of disrupted sleep may be inconvenient, the resulting daytime sleepiness can cause serious cognitive impairments. It reduces a person’s attention, as well as their learning and processing. A lack of sleep has also been found to induce effects that are similar to being drunk, which slows down thinking and reaction time.

Just struggling to stay alert can, in itself, cause sweeping problems for thinking, but research also indicates that there are selective impacts of poor sleep on mental function. This means that insufficient or disrupted sleep causes more harm to certain parts of the brain with distinct effects on different types of cognition.

Studies of the selective impact of sleep on types of thinking do not always generate consistent results. This may be the result of differences in the people in the studies, how their sleep is changed in the research, or how cognitive effects are measured. Nevertheless, there are some general findings about ways that poor sleep may impair intellectual performance.

There are strong indications that sleep and memory are closely linked. Lack of sleep hinders working memory, which is necessary to remember things for immediate use.

Both NREM and REM sleep appear to be important for broader memory consolidation, which helps reinforce information in the brain so that it can be recalled when needed. For example, NREM sleep has been linked with formation of declarative memory, which includes things like basic facts or statistics, and REM sleep is believed to boost procedural memory such as remembering a sequence of steps.

Poor sleep impairs memory consolidation by throwing off the normal process that draws on both NREM and REM sleep for building and retaining memories. Studies have even found that people who are sleep deprived are at risk of forming false memories. Fragmented sleep has also been found to negatively affect memory even if a person gets plenty of total hours of sleep.

On top of the consequences for memory, poor sleep detracts from other cognitive tasks. It diminishes placekeeping, which includes the ability to carry out instructions. Motor skills, keeping rhythm, and even some types of speech are worsened without proper sleep.

Some studies have found lack of sleep to hinder cognitive flexibility, reducing the ability to adapt and thrive in uncertain or changing circumstances. A major reason this occurs is rigid thinking and “feedback blunting” in which the capacity to learn and improve on-the-fly is diminished.

Another way that poor sleep impairs thinking is by altering how emotional information is understood. When learning something new, analyzing a problem, or making a
decision, recognizing the emotional context is often important. However, insufficient sleep — which frequently affects mood — impedes the ability to properly process this emotional component of information.

In many cases, this disrupted emotional response impairs judgment. People who don’t get sufficient sleep are more likely to make risky choices and to focus on a potential reward rather than downsides. This can become negatively reinforcing because a lack of sleep limits our ability to learn from these mistakes since the normal method of processing and consolidating emotional memory is compromised.

Creativity is another aspect of cognition that is harmed by sleeping problems. Connecting loosely associated ideas is a hallmark of creativity, and this ability is strengthened by good sleep. NREM sleep provides an opportunity for information to be restructured and reorganized in the brain, while new ideas and links between thoughts often emerge during REM sleep. These processes enable insight, a core element of innovation and creative problem-solving.

Limited or restless sleep can also indirectly affect cognition because of other problems that they cause. For example, migraine sufferers are more likely to have morning headache attacks when they don’t get enough sleep, and lack of sleep can increase the risk of the infections like the common cold. Sleep deprivation may worsen symptoms of mental health conditions like anxiety and depression. These and numerous other physical and mental health issues are shaped by the quality of our sleep, and may affect a person’s attention and concentration.

The existing research strongly supports the notion that poor sleep detracts from effective thinking. Without quality sleep, people are more likely to make errors, fail to take in new information, suffer deficits in memory, or have impaired decision-making.

As a result, poor sleep can harm intellectual performance, academic achievement, creative pursuits, and productivity at work. The cognitive impacts of poor sleep can also create health risks, including life-threatening dangers from drowsy driving or operating heavy machinery without adequate sleep.

What Are the Long-Term Impacts of Poor Sleep on Cognition?

The most obvious cognitive effects of poor sleep can be felt immediately, but mounting evidence shows that sleep influences the long-term risks of cognitive decline and dementia.

An analysis of more than 25 observational studies found a considerably higher risk ofcognitive impairment and Alzheimer’s dementia in people with sleep problems. In fact, that analysis estimated that as many as 15% of cases of Alzheimer’s dementia are attributable to poor sleep.

Research shows that sleep helps the brain conduct important housekeeping, such as clearing out potentially dangerous substances like beta amyloid proteins. In Alzheimer’s dementia, beta amyloid forms in clusters, called plaques, that worsen cognitive function. Studies have found that even one night of sleep deprivation can increase the amount of beta amyloid in the brain.

This is one possible explanation for why insufficient sleep and sleep fragmentation have been associated with cognitive decline and dementia. Furthermore, in people already diagnosed with dementia, poor sleep has been linked to a worse disease prognosis.

Are the Impacts of Poor Sleep on Thinking the Same for Everyone?

Not everyone is affected by poor sleep in the same way. Studies have found that some individuals may be more inclined to have cognitive impairment from sleep deprivation, and this may even have a genetic component.

Research has generally discovered that adults are better at overcoming the effects of sleep deprivation than younger people. Teens are considered to be especially high-risk for detrimental effects of poor sleep on thinking, decision-making, and academic performance because of the ongoing brain development occurring during that age.

Some studies have also found that women are more adept at coping with the effects of sleep deprivation than men, although it is not yet clear if this is related to biological factors, social and cultural influences, or a combination of both.

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