No association with napping
Unlike another of Dr. Gao’s studies that was conducted in a much older population, napping was not a risk factor for Alzheimer’s disease in the current study’s younger participants. It could be that the impacts of different sleep traits on health outcome change with age, Dr. Gao said, or this could represent a limitation of using self-reported sleep measures as opposed to objective and/or quantitative measures, such as actigraphy. The reasons for napping, which differ around the world with the habit being common in certain parts, may also help explain differences in observed associations.
Although the investigators tried to control for comorbidities and medication use, there “most certainly” could be a reverse causation at work. For example, sleeping too much could be both a cause and a symptom of dementia. Dr. Gao noted that sleep disturbances often become more prevalent with dementia, and sleeping too much or complaining of daytime sleepiness may be a result of preclinical Alzheimer’s disease. Even if there is a reverse causation, however, the average time to Alzheimer’s disease diagnosis was over 6 years in this study. “This may be a significant window of time to intervene,” he said.
To improve sleep health, he recommends going to bed and waking at similar times every day, avoiding caffeine or alcohol close to bedtime, limiting screen time before bed, dimming lights, and reducing noise.
It’s also important to have sleep apnea treated. “While more studies are needed, it’s generally believed that addressing the pauses in breathing, the apnea episodes, will help reduce cardiovascular health risks such as obesity, high blood pressure and heart failure. All are known to be strongly linked to dementia risk,” Dr. Gao said.
Results from an assessment of 100,000 actigraphy records from a subset of the same population are expected soon and will add objective confirmation of these self-reported results, he added.
Unique, powerful
Commenting on the findings, Alberto Ramos, MD, associate professor of clinical neurology and research director of the sleep medicine program at the University of Miami, called the study “unique” and “powerful” because of its prospective design and large sample size.
“Another strength of the study was that it included a population-based sample as opposed to one from a memory or sleep clinic where people already have symptoms or are already sick,” said Dr. Ramos, who was not involved with the research.
In addition, while most studies that have linked sleep disturbances with dementia risk have been in older adults, this study’s population was middle-aged to start out, he noted.
Dr. Gao and Dr. Ramos reported no relevant financial relationships. Although Dr. Gao’s lab receives funding from the National Institutes of Health, the BrightFocus Foundation, the University of Manchester, the Medical Biodynamics Program, Brigham and Women’s Hospital, and the Broad Institute, the study itself does not have its own specific funding.
A version of this article originally appeared on Medscape.com.