In a recent blog post, I discussed how beneficial sleep is for memory function. But sleep isn’t just good for your memory. It can actually reduce the risk of dementia and death. Although it has been known for some time that people with dementia often have poor, fragmented sleep, two new studies suggest that if you don’t get enough sleep, you’re at an increased risk for dementia.
Get six to eight hours of sleep every night
In the first study, researchers from Harvard Medical School looked at more than 2,800 people aged 65 and over who participated in the National Health and Aging Trends Study to examine the association between their self-report on sleep characteristics in 2013 or 2014 and their development of dementia and / or death five years later. The researchers found that people who slept less than five hours a night were twice as likely to develop dementia and twice as likely to die as those who slept six to eight hours a night. This study controlled demographics such as age, marital status, race, education, health status, and body weight.
In the second study, researchers in Europe (including France, the United Kingdom, the Netherlands, and Finland) looked at data from nearly 8,000 participants from another study and found that they consistently slept six hours or less at ages 50, 60, and 70 years old with a 30% increase in the risk of dementia compared to a normal sleep of seven hours. The mean age at which dementia was diagnosed was 77 years. This study controlled sociodemographic, behavioral, cardiometabolic, and mental health determinants, even though most of the participants were know, better educated, and healthier than the general population. In addition, about half of the participants had their sleep time measured objectively with a portable accelerometer – a device that tracked their sleep using body movements – which confirmed the questionnaire data.
Insufficient sleep in midlife can lead to dementia
What is new here is that insufficient sleep in mid-life increases the risk of dementia. There are many reasons for poor sleep in middle age: shift work, insomnia, due diligence, anxiety, and pressing deadlines to name a few. While not all of them are controllable, some are. For example, if you currently only sleep four to five hours because you work late every night, you may want to change your habits. Otherwise you run the risk of developing dementia until you retire.
This relationship between middle-aged sleep and late-life dementia is important not only from a clinical but also from a scientific point of view. It has always been a chicken and egg problem trying to interpret the relationship between poor sleep and dementia. Was it really bad sleep that caused dementia or just early symptoms of dementia that caused bad sleep? If we look at people who were originally screened in middle age – some as early as the age of 50 – we now have greater certainty that poor sleep may increase the risk of developing dementia for 25 years or more in the future.
Flush your brain while you sleep
While it is not fully understood why insufficient sleep increases your risk of dementia, one possible reason lies in the deposition of the Alzheimer’s protein, beta-amyloid. Beta amyloid is the protein that agglomerates and clumps to form Alzheimer’s plaques. No one is completely sure what its normal function is, although there is increasing evidence that it is involved in the brain’s defense against invading microorganisms.
During the day, we all make some of this beta amyloid protein in the brain. However, when we sleep, the brain cells and their connections actually shrink. This shrinking allows more space between brain cells so that beta-amyloid and other substances that build up during the day can be washed away.
So the theory is that if you don’t get enough sleep, your brain doesn’t have enough time to drain beta-amyloid and other substances. These substances then continue to build up day by day until they cause dementia.
The good news
The good news is that you can reduce your risk of dementia by getting enough sleep. A study by researchers from Toronto and Chicago looked at people with an increased genetic risk of developing Alzheimer’s. They found that better sleep not only reduced the likelihood of clinical Alzheimer’s disease, but also reduced the development of entanglement pathology in the brain – another substance that builds up in Alzheimer’s disease.
The final result
Sleep isn’t just an annoying break between the important aspects of our waking life. Just like eating and exercising properly, sleep is absolutely necessary for good brain health. These two new studies show that the harmful effects of insufficient sleep can begin by age 50 (if not earlier), leading to early dementia and death. The good news, however, is that you can reduce your risk of dementia by getting six to eight hours of sleep each night. Avoid sleeping pills as they won’t give you the deep sleep you need. If you have trouble sleeping, non-pharmacological approaches are best.