A new study has found that longer and more frequent daytime naps were linked to an increased risk of Alzheimer's dementia in older adults.
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The study from researchers at Brigham and Women’s Hospital in Boston was published on Thursday in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
Higher risk of Alzheimer's
The scientists tracked the daytime sleeping habitsof more than 1,000 elderly 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.
Overall, participants who napped more than an hour per day had a 40% increased risk of developing Alzheimer’s than those who napped less than an hour per day. Participants who napped at least once per day also had a 40% increased risk of developing Alzheimer’s than those who didn't.
The research could help resolve conflicting results of the impacts of napping on cognition in elderly people. While some previous studies have found that daytime napping has benefits on acute cognitive performance, mood, and alertness, others have underscored the adverse outcomes on cognitive performance.
A vicious cycle
The relationship between daytime napping and Alzheimer’s has been described as a 'vicious cycle.' Lead author of the study who works in the Medical Biodynamics Program at the Brigham’s Division of Sleep and Circadian Disorders, Dr. Peng Li, said:
The vicious cycle we observed between daytime sleep and Alzheimer’s disease offers a basis for better understanding the role of sleep in the development and progression of Alzheimer’s disease in older adults.
The authors found that not only does excessive daytime napping increase the risk of Alzheimer’sdementia, but also that an Alzheimer’s diagnosis 'sped up the increase' in daytime napping during the ageing process, the Brigham said.
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Dr. Li said:
Our results not only suggest that excessive daytime napping may signal an elevated risk of Alzheimer’s dementia, but they also show that faster yearly increase in daytime napping may be a sign of deteriorating or unfavored clinical progression of the disease.
Assistant professor of psychiatry at the University of California San Francisco, Dr Yue Leng, said:
It might be a signal of accelerated ageing. 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.
