Another Benefit of a Good Night’s Sleep: Improved Cognitive Function

Studies show that getting the right amount of quality sleep is valuable for brain health.

Young beautiful dark-haired woman asleep in bed

Medically reviewed in September 2022

Updated on September 9, 2022

Want a simple way to stay as mentally sharp as someone 4 to 7 years younger? Aim to get the right amount of sleep.

In our sleep-deprived times, doing so is, of course, easier said than done, and many Americans fall short of the recommended 7 to 9 hours per night. But the benefits for your brain and overall well-being make it worth the effort.

Some extra motivation: Several large studies of middle-aged people reveal that those who consistently slept the optimal amount scored the best on cognitive-function tests and had less severe cognitive decline over time.

What the studies showed
In one 2011 study published in the journal Sleep, people reported how many hours of sleep they got on an average weeknight, then did so again more than five years later. On both occasions, they also took tests measuring various aspects of cognitive function, including memory, reasoning, and vocabulary.

The upshot? Those who fell short of 6 to 8 hours of sleep ended up with lower test scores. Interestingly, getting too much sleep was problematic, too. Those who got more than 8 hours also scored poorly on several tests. All told, the lower test scores approximated an increase in one’s age of 4 to 7 years.

More recently, a 2020 study published in JAMA Network Open looked at the sleep habits of more than 20,000 people in England and China. The researchers found that the cognitive scores of people who logged 4 hours or fewer or 10 hours or more of sleep per night declined more rapidly than the scores of folks logging that sweet spot of approximately 7 hours per night.

Sleep and your brain
It's not clear why too little or too much sleep affects the brain. It may be the case that people who have underlying cognitive issues to begin with are more prone to sleeping too little or too much, though it’s unknown which causes which. 

What we do know is that sleep trouble is linked to everything from depression to heart disease, stroke, high blood pressure, kidney disease, obesity, and diabetes. This may be because sleep affects levels of a host of different hormones and chemicals that have effects throughout the body. It appears as if those changes in hormones and body chemicals have an impact on your brain power, too.

So, if you’re working with a sleep deficiency, try to optimize your sleep schedule to give yourself that 7 to 9 hours a night. If you still find yourself consistently sleeping fewer than 7 or more than 9 hours a night, consider speaking with a healthcare provider about how to get your slumber back on track.

Article sources open article sources

NIH: National Heart, Lung, and Blood Institute. What Are Sleep Deprivation and Deficiency? Last updated March 24, 2022.
Ferrie JE, Shipley MJ, Akbaraly TN, Marmot MG, Kivimäki M, Singh-Manoux A. Change in sleep duration and cognitive function: findings from the Whitehall II Study. Sleep. 2011;34(5):565-573.
Ma Y, Liang L, Zheng F, Shi L, Zhong B, Xie W. Association between sleep duration and cognitive decline. JAMA Netw Open. 2020;3(9):e2013573.
Centers for Disease Control and Prevention. High Blood Pressure: How Does Sleep Affect Your Heart Health? Last reviewed January 24, 2021.
Liu Y, Wheaton AG, et al. Prevalence of Healthy Sleep Duration among Adults — United States, 2014. MMWR Morb Mortal Wkly Rep 2016;65:137–141.

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