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You’ve heard it for years—eight hours of sleep is key to good health. However, new research suggests otherwise.
A recent study published in Nature Aging found that seven hours of sleep may actually be best. In their study, the researchers evaluated sleep time as it related to cognitive function, the structure of the brain, and mental health.
Researchers examined the sleep cycles, cognitive ability, and mental health of close to 500,000 adults, sourcing data from the UK Biobank, a large-scale collection of genetic and medical data. All of the participants fell between the ages of 38 and 73. (Sorry, Gen-Z, your sleep study will come.) The study also relied on participant’s answers to questions regarding their sleep habits and mental health, as well as cognitive tests and brain imaging of close to 40,000 participants as well.
In the study, researchers discovered too much or too little sleep negatively impacted the participants’ cognitive function (i.e. their memory and problem-solving). Those who got seven hours of sleep a night demonstrated the best brain function—as well as better overall emotional wellbeing.
How sleep connects to your cognitive function
When it comes to your sleep, prioritize quality over quantity. The researchers noted that the strength of a seven-hour night may lie in the lack of sleep interruptions. At seven hours, you’re able to tap into slow-wave sleep, also known as your deep sleep. According to the American Sleep Association, this type of sleep allows you to process and consolidate memories in your brain.
If you’ve ever pulled an all-nighter or suffered from insomnia, this concept may resonate. The ramifications of your sleep-deprived state show up almost immediately. You may find yourself forgetting small things, or just struggling to think. It’s not in your head. (Well, it sort of is.) Without sleep, your brain doesn’t have an opportunity to consolidate critical memories. You haven’t given your brain the tools to do so.
Over time, sleep deprivation can have even larger consequences for your memory. A small study conducted by the National Institutes of Health in 2018 found an increased presence of beta-amyloid, a protein associated with Alzheimer’s Disease, in sleep-deprived participants.
Both studies call for more evidence in order to definitively draw causal links between sleep time and brain health. However, it’s clear that your sleep plays critical a role in your day-to-day memory processing.
How your sleep impacts your mental health
According to the study, getting more or less than seven hours of sleep a night also resulted in an increase in symptoms tied to anxiety and depression.
You’re likely familiar with the concept of waking up on the wrong side of the bed feeling out-of-sorts. A sleep-deprived night can lead you to feel moody, angry, sad, or anxious. And the findings in the Nature Aging study support this shift. Researchers found that participants who slept for seven hours a night on a regular basis had better mental health than participants who slept more or less than seven hours.
How to get a good night’s sleep
We’ve all been there. If you’re tossing and turning all night, you may want to try calming down with a sleep meditation or some soothing yoga poses. Restorative yoga practices can help calm your nervous system and bring you into a more relaxed state. (Try the restorative yoga poses Jonathan Van Ness uses to get himself back to sleep.)
If you’re just a night owl—someone who tends to go to bed later and seems to need less sleep—you may have Delayed Sleep Phase Disorder (DSPD). If your circadian rhythms are off, this may cause you to go to bed late. A provider may prescribe melatonin supplements or light exposure therapy. Practice good sleep hygiene by avoiding caffeine or alcohol in the evening, moving your TV and work materials out of your bedroom, and exercising in the morning instead of at night.