For people with sleep deprivation, insomnia, sleep apnea, or other conditions that prevent getting adequate rest, short-term daytime cognitive impairment is common. In addition, multiple studies have linked poor sleep with longer-term cognitive decline, including the development of dementia and Alzheimer’s disease.

Better sleep can promote sharper thinking and may reduce the likelihood of age-related cognitive decline. There is evidence that improving sleep can offer a practical way to enhance both short and long term cognitive performance. Researchers and public health experts are increasingly viewing that good sleep may reduce the longer-term likelihood of developing Alzheimer’s dementia.

How Healthy Sleep Affects the Brain

A typical night of sleep includes four to six sleep cycles that last from 70 to 120 minutes each. Both the brain and body experience distinct changes during these cycles that correspond to individual stages of sleep.

• During NREM stages, brain activity slows overall, but there remain pulses of specific types of brain waves. This pattern of brain waves is most pronounced in stage 3 NREM sleep, which is also known as slow-wave sleep or deep sleep.

• REM sleep is marked by an uptick in brain activity. In many ways, the brain’s activity during REM sleep is similar to being awake. REM sleep is known for more vivid and involved dreaming.

• Cycling through both NREM and REM stages is normal, with REM sleep being more concentrated in the second half of the night. During each part of this process, different chemicals in the brain become activated or deactivated to coordinate rest and recovery.

• It is believed that this pattern of cycling through phases facilitates mental recovery, and unlocks cognitive benefits related to attention, thinking, and memory

Unhealthy Sleep and the Brain

• Poor sleep can take many forms. It can be caused by short sleep duration and/or fragmented sleep. Both insufficient and interrupted sleep make it difficult to progress through sleep cycles in a normal, healthy way.

• Without sleep, the brain struggles to function properly. Because they don’t have time to recuperate, neurons become overworked and less capable of optimal performance.

• Sleep helps the brain clear out potentially dangerous substances like beta amyloid proteins, which cluster in plaques and worsen cognitive function. Studies have found that even one night of sleep deprivation can increase the amount of beta amyloid in the brain.

• The short-term implications of poor sleep on the brain and cognition can be the result of simply pulling an all-nighter, while those with chronic sleep problems may see their day-to-day tasks affected.

How Unhealthy Sleep Affects the Brain Over the Short Term

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. 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.

• Sleep deprivation may worsen symptoms of mental health conditions like anxiety and depression.

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

• Research indicates that there are selective impacts of poor sleep on mental function. Insufficient or disrupted sleep causes more harm to certain parts of the brain with distinct effects on different types of cognition.

• There are strong indications that sleep and memory are closely linked. 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 found that sleep deprivation increases the risk of forming false memories. Fragmented sleep has also been found to negatively affect memory even if there is adequate total sleep.

• Poor sleep detracts from other cognitive tasks. It diminishes place keeping, which includes the ability to carry out instructions. Motor skills, keeping rhythm, and even some types of speech are worsened without proper sleep.

• Poor sleep can alter how emotional information is understood and the ability to appropriately recognise emotional context. It also frequently affects mood.

• 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 reorganised 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.

How Unhealthy Sleep Affects the Brain Over the Long Term

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 of cognitive 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.

• In people already diagnosed with dementia, poor sleep has been linked to a worse disease prognosis.

• Studies have also found that people with sleep apnea have a higher risk of developing dementia.

Sources: The Sleep Foundation | Wikipedia | National Library of Medicine