The New York Times
Too little sleep in middle age can increase the risk of dementia, the study finds
Can too little sleep increase your chances of dementia? For years, researchers have pondered this and other questions about how sleep is associated with cognitive decline. Answers were evasive because it is difficult to know whether insufficient sleep is a symptom of the brain changes underlying dementia – or that it may be contributing to it. Now, a major new study reports some of the most compelling findings yet suggested that people who do not get enough sleep in their 50s and 60s are more likely to get dementia as they get older. Sign up for The Morning Newsletter of the New York Times The research, published Tuesday in the journal Nature Communications, has limitations but also several strengths. This followed for about 25 years in Britain, about 50 years old. It found that those who consistently reported sleeping six hours or less on an average weekday night were about 30% more likely than people diagnosed with seven hours of sleep (defined as ‘normal’ sleep) almost three decades later. . . “It is really unlikely that this sleep was a symptom of dementia almost three decades earlier. It is therefore an excellent study to provide strong evidence that sleep is really a risk factor,” said Dr. Kristine Yaffe, a professor of neurology and psychiatry, said. at the University of California, San Francisco, who was not involved in the study. It is known that changes in pre-dementia, such as the accumulation of proteins associated with Alzheimer’s, begin about 15 to 20 years before people display memory and thinking problems, so sleep patterns within the timing can be considered an emerging effect of the disease. ‘It asked a question about chicken or egg which is the first place, the sleep problem or the pathology,’ says dr. Erik Music, a neurologist and co-director of the Center for Biological Rhythms and Sleep at Washington University in St. Louis. who were not involved in the new research. “I do not know that this study necessarily concludes the agreement, but it comes closer because there are many people who were relatively young,” he said. “There is a good chance that they catch middle-aged people before they have Alzheimer’s disease pathology or plaques and tangles in their brain.” Based on medical records and other data from a prominent study of British civil servants named Whitehall II, which began in the mid-1980s, researchers looked at how many hours 7,959 participants said they slept in reports between 1985 and 2016 was submitted six times. At the end of the study, 521 people at an average age of 77 were diagnosed with dementia. The team was able to adapt to different behaviors and characteristics that would affect people’s sleep pattern or dementia risk, said a study author, Séverine Sabia. an epidemiologist at Inserm, the French public health research center. These include smoking, alcohol use, how physically active people were, body mass index, fruit and vegetable consumption, education level, marital status and conditions such as high blood pressure, diabetes and cardiovascular disease. To further clarify the sleep-dementia relationship, researchers excreted people who had mental illnesses before age 65. Depression is considered a risk factor for dementia and ‘mental health disorders are very strongly linked to sleep disorders’, Sabia said. The analysis of the study of participants without mental illness found a similar association between short sleepers and increased risk of dementia. The correlation also determined whether or not people used sleeping pills and whether they had a mutation called ApoE4 that makes people more likely to develop Alzheimer’s, Sabia said. The researchers found no general difference between men and women. “The study has a modest but I would say an important link between short-term sleep and dementia risk,” said Pamela Lutsey, an associate professor of epidemiology and community health at the University of Minnesota who was not involved in the research. not. ‘Short sleep is very common, and even if it is modestly associated with dementia, it can be important on a social level. Short sleep is something we have control over, something you can change. However, as with other research in this area, the study has limitations that prevent it from proving that insufficient sleep can cause dementia. Experts believe that most of the sleep data was self-reported, a subjective measure that is not always accurate. At one point, nearly 4,000 participants did have the sleep duration using accelerometers, and that the data were consistent with their self-reported sleep times, the researchers said. However, this quantitative measure came late in the study, when participants were about 69, which made it less useful than when obtained at younger ages. In addition, most participants were white and better educated and healthier than the British population. And if they relied on electronic medical records for dementia diagnoses, researchers would have missed some cases. They also could not identify exact types of dementia. “It is always difficult to know what conclusions can be drawn from these types of studies,” wrote Robert Howard, a professor of geriatric psychiatry at University College London, one of several experts who commented on the study to Nature Communications. has. “Insomnia – which probably does not need anything else to chew over in bed,” he adds, “should not worry that they are on their way to dementia unless they sleep immediately.” There are compelling scientific theories as to why too little sleep can exacerbate the risk of dementia, especially Alzheimer’s. Studies have found that the cerebrospinal fluid levels of amyloid, a protein that clumps together in Alzheimer’s plates, ‘rise when you put people to sleep,’ Music said. Other studies on amyloid and another Alzheimer’s protein, tau, suggest that ‘sleep is important in removing proteins from the brain or limiting production,’ he said. One theory is that the more people are awake, the longer their neurons are active and the more amyloid is produced, Music said. Another theory is that fluid flowing into the brain during sleep helps eradicate excess protein, so insufficient sleep means more protein buildup, he said. Some scientists also think that it may be important to remove time during certain sleep phases to cleanse proteins. Lutsey said that too little sleep can also function indirectly, fueling the conditions that are known dementia risk factors. “Think of someone who stays up late and eats snacks, or because they have little sleep, they have low motivation for physical activity,” she said. “It can expose them to obesity, and then things like diabetes and high blood pressure that are pretty strongly linked to the risk of dementia.” Another theory is’ a shared genetic link, ” Yaffe said, ” genetic pathways or profiles associated with shorter sleep and increased risk for Alzheimer’s. ” She and others have said that it is also possible that the sleep-dementia relationship is ‘two-way’, with poor sleep promoting dementia, further reducing sleep, exacerbating dementia. Experts seem to agree that it is a challenge to investigate the link between sleep and dementia and that previous studies have sometimes yielded confusing findings. In some studies, people who sleep too long (usually measured as nine hours or longer) appear to be at greater risk of dementia, but a number of studies were smaller or had older participants, experts said. In the new study, the results indicate increased risk for long-term sleepers (defined as eight hours or longer because there were not enough nine-hour sleepers, Sabia said), but the association was not statistically significant. Experts said they could not think of scientific explanations as to why long sleep would increase the risk of dementia and that it could reflect a different underlying health condition. The new study also looked at whether people’s sleep has changed over time. Sabia apparently had a slightly increased risk of dementia in people who switched from short to normal sleep, a pattern that she said may reflect that they slept too little at age 50 and later needed more sleep as a result. of dementia. So, if short sleep is a culprit, how can people get more zzz’s? “In general, sleeping pills and many other things do not give you that deep sleep,” Yaffe said. And ‘we really want deep sleep, because it seems like it’s the time to tidy things up and fix them.’ She said naps are okay to catch up on missed sleep, but to get a good night’s sleep should make naps unnecessary. People with sleep disorders or apnea should consult sleep specialists, she said. Lutsey said avoiding a regular sleep schedule, caffeine and alcohol before bedtime, and removing phones and computers from the bedroom, is one of the guidelines for the Centers for Disease Control and Prevention. But much about sleep remains enigmatic. The new study “provides fairly strong evidence that sleep is important in middle age,” Music said. “But we still have a lot to learn about it and how the relationship actually occurs in people and what to do about it.” This article originally appeared in The New York Times. © 2021 The New York Times Company