The results of a large recent study, tracking thousands of people from age 50 upwards, suggests those who sleep six hours or less a night are more likely to develop dementia in their late 70s. Thus it is advisable to sleep for more than six hours a night. Mental health disorders are known to be quite strongly linked with sleep disturbances.

The research which was published in the journal Nature Communications, studied nearly 8,000 people in Britain for about 25 years. All the subjects were 50 years old or older.

For many years, scientists have pondered whether getting too little sleep could affect physical and mental health and questions about how sleep relates to cognitive decline. Figuring this out had been difficult because it was hard to establish a relationship between insufficient sleep and the physiological changes that occur in the brain that underline the development of dementia.

The large new study highlights very persuasive new findings that clearly suggest that people who don’t get enough sleep in their 50s and 60s may be more likely to develop dementia when they are older.

Precisely 8,000 individual subjects (people) were followed in Britain over a period of about 25 years, beginning when they were 50 years old. The findings from the study show that those who consistently reported sleeping six hours or less on an average weeknight were about 30 percent more likely than individuals who regularly got seven hours sleep (defined as “normal” sleep in the study) to be diagnosed with dementia nearly three decades later.

Dr. Kristine Yaffe, a professor of neurology and psychiatry at the University of California, San Francisco, Said “It would be really unlikely that almost three decades earlier, this sleep was a symptom of dementia, so it’s a great study in providing strong evidence that sleep is really a risk factor,”.

Accumulations of proteins associated with Alzheimer’s are known to begin about 15 to 20 years before people exhibit memory and thought coordination problems, these characterize the Pre-dementia changes in the brain. So sleep patterns within that time frame could be considered an emerging effect of the disease. According to Dr. Erik Musiek, a neurologist and co-director of the Center on Biological Rhythms and Sleep at Washington University in St. Louis, "that has posed a chicken or egg question of which comes first, the sleep problem or the pathology,”

“I don’t know that this study necessarily seals the deal, but it gets closer because it has a lot of people who were relatively young,” he said. “There’s a decent chance that they are capturing people in middle age before they have Alzheimer’s disease pathology or plaques and tangles in their brain.”

A review of data from a prominent study of British civil servants in the mid-1980s, called Whitehall II, researchers tracked how many hours 7,959 participants said they slept in reports filed six times between 1985 and 2016. By the end of the study, 521 people had been diagnosed with dementia at an average age of 77.

According to the New York Times several behaviors and characteristics that account influence individual sleep patterns were considered in the study. These include smoking, alcohol consumption, level of physical activity, body mass index, fruit and vegetable consumption, education level, marital status and conditions like hypertension, diabetes and cardiovascular disease, whether or not people were taking sleep medication and whether or not they had a mutation called ApoE4 that makes people more susceptible to develop Alzheimer’s disease. Depression is also considered a risk factor for dementia.

The researchers separated out people who had mental illnesses before age 65 and the study’s analysis of participants without mental illnesses found a similar association between short-sleepers and increased risk of dementia.

The researchers found no general difference between men and women.

Short sleep is very common among the elderly and because of that, even if it’s modestly associated with dementia risk, it can be important at a societal level. Short sleep is something that we have control over, something that you can change.

Experts say most of the data in the research is self reported and therefore subjective. Thereby challenging the data accuracy. This is one of the limitations of the study.

At one point, nearly 4,000 participants did have sleep duration measured by accelerometers and that data was consistent with their self-reported sleep times, the researchers said. Still, that quantitative measure came late in the study, when participants were about 69, making it less useful than if it had been obtained at younger ages.

In addition, most participants were white and better educated and healthier than the overall British population. And in relying on electronic medical records for dementia diagnoses, researchers might have missed some cases. They also could not identify exact types of dementia.

Robert Howard, a professor of old age psychiatry at University College London says “Insomniacs — who probably don’t need something else to ruminate about in bed,” he added, “shouldn’t worry that they are heading for dementia unless they get off to sleep immediately.”

Studies have found that cerebrospinal fluid levels of amyloid, a protein that clumps into plaques in Alzheimer’s increase in people deprived of sleep. Sleep is also thought to be important for clearing proteins from the brain or limiting the production. One theory is that the more people are awake, the longer their neurons are active and the more amyloid is produced. Another theory is that during sleep, fluid flowing in the brain helps clear out excess proteins, so inadequate sleep means more protein buildup, he said. Some scientists also think getting sufficient time in certain sleep phases may be important for clearing proteins.

Too little sleep might also function indirectly, fueling conditions that are known dementia risk factors. Someone who commonly stays up too late to have snacks or because they get very little sleep, they have low motivation for physical activity will likely be predisposed to obesity, diabetes and hypertension all of which have been pretty robustly linked to dementia risk.

Another theory is “a shared genetic link,” genetic pathways or profiles that go along with both shorter sleep and increased risk of Alzheimer’s. It is also postulated that the sleep-dementia relationship is “bidirectional,” with poor sleep fueling dementia, which further reduces sleep, which worsens dementia.

The new study also examined whether people’s sleep changed over time. There appeared to be slightly increased dementia risk in people who shifted from short to normal sleep, a pattern which may reflect that they slept too little at age 50 and needed more sleep later because of developing dementia.

How Can You Get More Sleep:
Four out of five people say that they suffer from sleep problems at least once a week and wake up feeling exhausted. What you need is deep sleep and sleeping pills and a lot of other sleep aids don’t really give you deep enough sleep.

1) Naps are okay to catch up on missed sleep, but getting a good night’s sleep should make naps unnecessary. Scientists recommend people with sleep disorders or apnea should consult sleep specialists,

2) Having a regular sleep schedule, avoiding caffeine and alcohol before bedtime and removing phones and computers from the bedroom are recommended.

3) Stretching and meditative movement like yoga before bed can improve the quality of your sleep and the amount you sleep. Try short and calming routines like 11 stretches and exercises.

Reference : Belluck Pam, 2021, Sleeping Too Little in Middle Age May Increase Dementia Risk, Study Finds, Health, New York Times, accessed at®i_id=158757475&segment_id=55992&te=1&user_id=ae364b2b5baf8ea0ff972231bd5e2a8f.

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