The link between daytime napping and dementia
Sleep disturbance and daytime napping are known symptoms of mild to moderate Alzheimer’s disease and other forms of dementia in older adults. They often become more extreme as the disease progresses: Patients are increasingly less likely to fall asleep and more likely to wake up during the night and feel sleepy during the day.
To examine this link between daytime napping and dementia, my colleagues and I studied a group of 1,401 older adults with an average age of 81 participating in the Rush Memory and Aging Project, a longitudinal study examining cognitive decline and Alzheimer’s disease. The participants wore a watchlike device that tracked their mobility for 14 years. Prolonged periods of inactivity were interpreted as naps.
At the start of the study, approximately 75% of participants did not have any cognitive impairment. Of the remaining participants, 4% had Alzheimer’s and 20% had mild cognitive impairment, a frequent precursor to dementia.
While daily napping increased among all participants over the years, there were differences in napping habits between those who developed Alzheimer’s by the end of the study and those who did not. Participants who did not develop cognitive impairment had nap durations that averaged 11 extra minutes per year. This rate doubled after a mild cognitive impairment diagnosis, with naps increasing to 25 extra minutes per year, and tripled after an Alzheimer’s diagnosis, with nap durations increasing to 68 extra minutes per year.
Ultimately, we found that older adults who napped at least once or for more than an hour a day had a 40% higher chance of developing Alzheimer’s than those who did not nap daily or napped less than an hour a day. These findings were unchanged even after we controlled for factors like daily activities, illness and medications.