The Exact Amount of Sleep You Need Each Night To Cut Dementia Risk, According to a Sleep Medicine Doctor

No one feels their best after a night of poor sleep. When you wake up tired, there’s a good chance you’ll be more irritable than you would be otherwise. Paying attention becomes harder and it may take you three times as long to complete tasks that you would breeze through if you had gotten more rest.

Considering that even one night of poor sleep can wreck your mood and cognition, imagine what consistently not getting enough can do to your brain. It’s easy to underestimate the importance of shut-eye, but consistently getting enough is crucial to aging well. Not getting enough sleep increases the risk of depression as well as hypertension and negatively impacts immune health.

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If you consistently don’t get enough sleep, it also increases the risk of dementia, a health condition that impacts millions of Americans in the U.S. According to the National Institutes of Health, researchers estimate that 42% of Americans over age 55 will eventually develop dementia. 

While preventing dementia isn’t entirely in our control, there are ways you can significantly reduce your risk. Consistently catching enough Z’s is one especially powerful way to do exactly that. How many hours of sleep a night should you get for it to make a noticeable decrease in dementia risk? Parade talked to a sleep medicine doctor to find out. 

Related: Scientists Reveal This Many Daily Steps Could Cut Your Dementia Risk by 51%

Why Getting Enough Sleep Is Crucial for Brain Health

“Sleep is a vital restorative process for the brain,” explains Dr. Joshua Roland, MD, FAASM, a sleep medicine doctor and medical director at Dreem Health. He tells Parade that sleep is when the brain consolidates memories, regulates mood and cognitive function and clears away metabolic waste products that accumulate throughout the day.

Not getting enough shut-eye can truly be detrimental to brain health. “One of the most important is that insufficient sleep may impair the brain’s ability to clear proteins like beta-amyloid and tau, which are associated with Alzheimer’s disease,” Dr. Roland says. 

According to an article published in the journal Basic and Clinical Neuroscience, chronic sleep deprivation can increase tau protein concentrations (which are associated with Alzheimer’s) in the brain up to 50%. “While sleep alone does not determine whether someone develops dementia, long-term poor sleep is increasingly recognized as a meaningful risk factor,” Dr. Roland warns.

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How Much Sleep You Should Get Each Night To Lower Your Risk of Dementia

If you want to actively lower your risk of dementia, Dr. Roland says to aim to get at least seven hours of sleep each night, which is the amount backed by scientific research. Interestingly, sleeping more than nine hours a night is associated with a 63% higher risk of dementia; getting between seven and eight hours a night is the sweet spot when it comes to sleep and long-term brain health.

Dr. Roland emphasizes that it’s not just sleep quantity that’s important; sleep quality is too. “Someone who spends eight hours in bed but experiences frequent awakenings or untreated sleep disorders may still not be getting restorative sleep,” he says. 

Related: The Silent Symptom Most People Don’t Realize Could Be a Dementia Sign, According to Neurologists

A scientific study published in Sleepshows that fragmented sleep (waking up throughout the night) is associated with an increased risk of dementia. Dr. Roland explains that when sleep is interrupted in this way, it interferes with circadian rhythm, which plays a major role in regulating the body’s sleep-wake cycle, hormone release, metabolism and immune function. 

“Circadian disruption has been associated with impaired memory, reduced cognitive performance and changes in the brain that may increase vulnerability to neurodegenerative disease. We also know that many patients with dementia experience worsening circadian disruption as the disease progresses, so the relationship goes in both directions,” he says.

One common cause of fragmented sleep is sleep apnea. Since sleep apnea causes fragmented sleep, it’s not surprising that people with sleep apnea have a higher risk of dementia. “Untreated sleep apnea is also associated with high blood pressure, cardiovascular disease, stroke risk and inflammation, all of which can affect brain function and may contribute to an increased risk of cognitive decline and dementia. The encouraging part is that sleep apnea is treatable, and addressing it can significantly improve both sleep quality and overall health,” Dr. Roland says.

If you have sleeping problems that you haven’t addressed, consider this a wakeup call—no pun intended. It’s worth it to get to the root issue of why you aren’t sleeping well. In fact, it just might be the most powerful step you take in caring for your long-term health.

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Sources:

• Risk and future burden of dementia in the United States. National Institutes of Health.
• Dr. Joshua Roland, MD, FAASM, sleep medicine doctor and medical director at Dreem Health.
• Ahmadian, N., Hejazi, S., Mahmoudi, J., et al. (2018). Tau Pathology of Alzheimer’s Disease: Possible Role of Sleep Deprivation. Basic and Clinical Neuroscience. 9(5):307-316.
• Schneider, A. C., Moon, C., Whitaker, K., et al. (2022). Association of Sleep with Risk of Alzheimer’s Disease Mortality: NIH-AARP Diet and Health Study. Journal of Applied Gerontology. 41(4):1057-1065.
• Lim, A. S. P., Kowgier, M., Yu, L., et al. (2013). Sleep Fragmentation and the Risk of Incident Alzheimer’s Disease and Cognitive Decline in Older Persons. Sleep. 36(7):1027-1032.
• Ercolano, E., Bencivenga, L., Emiliana Palaia, M., et al. (2023). Intricate relationship between obstructive sleep apnea and dementia in older adults.GeroScience. 46(1):99-111.