An increase over time in naps among older people may signal higher chance of developing mild cognitive impairment or Alzheimer’s disease, according to a new US study.
Dr Yue Leng, an assistant professor of psychiatry at the University of California San Francisco, led research into excessive daytime sleeping and found it is likely to be a symptom rather than a cause of dementia.
“It might be a signal of accelerated ageing,” she said. “The main takeaway is if you didn’t used to take naps and you notice you’re starting to get more sleepy in the day, it might be a signal of declining cognitive health.”
Dr Leng and her colleagues tracked more than 1,000 people, with an average age of 81, over several years. Each year, the participants wore a watch-like device to track mobility for up to 14 days. Each prolonged period of non-activity from 9am to 7pm was interpreted as a nap.
The participants also underwent tests to evaluate cognition each year. At the start of the study, 76 per cent of participants had no cognitive impairment, 20 per cent had mild cognitive impairment and four per cent had Alzheimer’s disease.
For participants who did not develop cognitive impairment, daily daytime napping increased by an average of 11 minutes a year. The rate of increase doubled after a diagnosis of mild cognitive impairment to a total of 24 minutes, and nearly tripled to a total of 68 minutes after a diagnosis of Alzheimer’s disease.
Overall, participants who napped more than an hour a day had a 40% higher risk of developing Alzheimer’s than those who napped less than an hour a day, and participants who napped at least once a day had a 40% higher risk of developing Alzheimer’s than those who napped less than once a day.
The message? Keep an eye on the length of those siestas.
