For many years, researchers have looked at the question of whether there’s a link between the amount of sleep people get in middle age, and whether that correlates with whether or not they develop dementia when they get older.
Now, a new study indicates that there is, in fact, a connection.
The study is called “Association of sleep duration in middle and old age with incidence of dementia,” and it was published in the journal Nature Communications on Tuesday.
According to The New York Times, the study followed nearly 8,000 people in Britain over the course of 25 years, beginning when they were around 50 and continued into their 70s. The Times did point out that the numbers in the study were self-reported, especially when it came to the amount of sleep people were getting.
Per the Times, the study found that “those who consistently reported sleeping six hours or less on an average weeknight were about 30 percent more likely than people who regularly got seven hours sleep (defined as “normal” sleep in the study) to be diagnosed with dementia nearly three decades later.”
“Here we report higher dementia risk associated with a sleep duration of six hours or less at age 50 and 60, compared with a normal (7 h) sleep duration, although this was imprecisely estimated for sleep duration at age 70,” the study itself says. “Persistent short sleep duration at age 50, 60, and 70 compared to persistent normal sleep duration was also associated with a 30% increased dementia risk independently of sociodemographic, behavioural, cardiometabolic, and mental health factors. These findings suggest that short sleep duration in midlife is associated with an increased risk of late-onset dementia.”
The Whitehall II study is a well-known study of British civil servants, which has been going on since the 1980s and has had many practical applications over the years.
“The lowest dementia incidence per 1000 person-years was observed among those who slept 7 h per night, irrespective of the age at which sleep duration was measured,” the study said. “In analysis adjusted for sociodemographic factors, short sleep duration was associated with the higher risk of incident dementia at all ages… Further adjustment for health behaviours and cardiometabolic and mental health factors attenuated associations, but there remained an association for short sleep at 50 (hazard ratio (HR) = 1.22, 95% confidence interval (CI) = 1.01—1.48) and 60 years (HR = 1.37, 95% CI = 1.10—1.72). There was no clear evidence of an association between long sleep duration and incident dementia.”
A study from Harvard Medical School from August of 2015 had looked at the same question, The Women’s Health Initiative Memory Study (WHIMS) found that, per the title, “Too little—or too much—sleep linked to dementia risk.”
“The study found a modest, but I would say somewhat important association of short sleep and dementia risk,” said Pamela Lutsey, an associate professor of epidemiology and community health at the University of Minnesota, told the New York Times of the new study. “Short sleep is very common 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.”
Stephen Silver, a technology writer for The National Interest, is a journalist, essayist and film critic, who is also a contributor to The Philadelphia Inquirer, Philly Voice, Philadelphia Weekly, the Jewish Telegraphic Agency, Living Life Fearless, Backstage magazine, Broad Street Review and Splice Today. The co-founder of the Philadelphia Film Critics Circle, Stephen lives in suburban Philadelphia with his wife and two sons. Follow him on Twitter at @StephenSilver. Image: Reuters.