Sleep’s Role in Cognitive Health

Sleep is a regular biological process that everyone experiences. While scientists have yet to pinpoint a clear, explicit reason why humans sleep, it remains one of the body’s most important processes. The act of sleeping affects several systems and parts of the body, and lack of adequate sleep can have serious consequences.1 This is especially true when it comes to cognitive function.

Sleep can be split into four stages: stage one non-REM, stage two non-REM, stage three non-REM and REM. Stage one is the earliest stage, and consists of light sleep as the body relaxes from its waking state. Stage two also consists of light sleep in a more relaxed state. It is actually the longest stage of the sleep cycle. Stage three sees a transition into deep sleep, reflected by slower brain waves, breathing and heart rate. Finally, the fourth stage involves REM sleep, when the brain becomes somewhat active again — this is the time for vivid dreams. This cycle repeats throughout the night, lasting approximately 90 minutes each time. Sleep is controlled primarily by the body’s circadian rhythms, which affect several other bodily functions. While circadian rhythms conveniently align with the natural progression of day and night, the body can follow sleeping cues without relying on the sun and moon. The body also monitors the need for sleep through the process of sleep-wake homeostasis, which signifies when to sleep and how long to sleep for.1

High-quality sleep contributes to several of the brain and body’s essential processes. On a basic level, the Sleep Foundation reports, sleep supports attention and concentration, which contribute to better, more effective learning. On a more complex level, sleep plays a role in memory consolidation (the process of storing information in the brain for later recall), problem-solving (by enabling connections between ideas to form), neuroplasticity (the brain’s ability to adapt) and emotional processing (which affects interpretation of new information and judgment).2

As might be expected given sleep’s important role in the brain and body’s core processes, lack of adequate sleep negatively affects cognitive function. This is true for both short-term and long-term sleep deprivation. In fact, long-term sleep deprivation may increase the risk of cognitive decline and dementia. Looking through a short-term lens, lack of sleep can result in varying levels of fatigue or drowsiness, reduced reaction time, poor emotional processing and intellectual performance. Then, chronic lack of sleep — because of a sleep disorder or strenuous lifestyle — can impact memory, “housekeeping” (processes through which the brain clears toxins, such as the beta amyloid proteins associated with Alzheimer’s disease) and general mental health conditions.2

It’s important to prioritize getting sufficient high-quality sleep as often as possible to support long-term cognitive function. While there is no flawless method for guaranteeing perfect sleep, implementing certain practices may lead to better sleeping habits. For example, sleeping at a regular time every day and establishing a consistent sleep schedule can facilitate the process of falling asleep and waking up. Avoiding caffeine and excessive use of technology in the evening can help encourage sleep at reasonable hours and improve sleep quality throughout the night.2 Of course, ensuring that your sleeping environment is comfortable and undisruptive — by adjusting temperature, lighting and noise levels — is one of the easiest ways to improve sleep quality.3 Finally, experiencing difficulties falling or staying asleep for extended periods of time may be symptoms of a more serious sleep-related condition, so consulting with a specialist when possible and appropriate is always the best course of action.

As described, sleep is a fundamental part of human life. It is a process that benefits various bodily systems, including cognitive function and brain health. While it can be difficult to guarantee consistent high-quality sleep, making an active effort to improve sleep quality and duration yields both short-term and long-term health benefits.


  1. U.S. Department of Health and Human Services. (n.d.). Brain basics: Understanding sleep. National Institute of Neurological Disorders and Stroke. 
  2. How does lack of sleep affect cognitive impairment?. Sleep Foundation. (2023, April 20).
  3. Centers for Disease Control and Prevention. (2022, September 13). Tips for better sleep. Centers for Disease Control and Prevention.