November 16, 2022
What time you go to bed, and how much time you spend in bed, may be tied to your risk of developing Alzheimer’s disease, according to a new report. The findings add to growing evidence linking sleep patterns with the onset of Alzheimer’s disease.
The study looked at 1,982 older adults living in rural China who were part of an ongoing study of aging and brain health. Their average age was around 70. All were free of dementia at the study’s start.
Over the next four years, they were given medical checkups and regular assessments of memory and thinking skills. They also filled out detailed questionnaires about their sleep patterns. During that time, 97 were diagnosed with dementia, including 68 with Alzheimer’s disease.
The researchers found that the risk of Alzheimer’s disease or other forms of dementia was 69 percent higher in people who slept more than eight hours a night compared to those who slept seven to eight hours a night. The dementia risk was twice as high in those who went to bed before 9 at night, compared to those who went to bed at 10 p.m. or later.
Even in those who did not develop dementia, spending many hours in bed was tied to an increased risk of declines in memory and thinking skills. This risk factor was noted in those ages 60 to 74 and in men. The study did not look at people younger than 60.
The researchers, from Shandong University, considered such factors as age, education level, body mass index, alcohol and smoking habits, high blood pressure, diabetes, stroke and whether they carried the APOE-e4 genotype, all of which can affect Alzheimer’s risk.
They found that sleep problems were independently associated with “incident dementia” and Alzheimer’s disease. “This suggests that cognitive function should be monitored in older adults who report prolonged time in bed and advanced sleep timing,” they wrote.
They noted that “long sleep duration has been associated with global brain atrophy,” or brain wasting, as well as increase in the number of white matter hyperintensities, abnormal brain lesions picked up on MRI brain scans that are linked to an increased risk of Alzheimer’s disease. Excessive sleep time has also been tied to “proinflammatory biomarkers, such as interleukin-6 and C-reactive protein, which may be the pathways linking long sleep duration to dementia,” the authors noted. Inflammation, and not only in the brain, is increasingly recognized as a risk factor for chronic diseases of aging, including dementia. The findings were published in the Journal of the American Geriatrics Society.
The findings add to growing research linking sleep disturbances with Alzheimer’s disease risk. Being excessively tired during the daytime and taking frequent naps in midlife has been associated with an increased risk of Alzheimer’s disease. Other research suggests that poor sleep may disrupt our circadian rhythms and impair the ability of immune cells to clear the brain of toxic beta-amyloid, the protein that clumps together to form the telltale plaques of Alzheimer’s disease.
Healthy older adults who sleep soundly tend to have less buildup of beta-amyloid in the brain. Deep sleep appears to act as a kind of cleaning system, ridding the brain of toxic debris. Other studies have shown that men and women who slept less than six hours a night in their 50s and 60s were also at increased risk of developing dementia when they were older.
Similarly, sleep apnea, a common nighttime disorder marked by loud snoring and disrupted sleep, has been linked to memory decline and dementia. Sleep apnea may be particularly prevalent in people with Alzheimer’s disease. If you suspect that breathing problems during sleep may be contributing to memory and thinking problems, it is important to discuss this with your doctor.
Sleep problems generally increase with advancing age and, as these and other studies show, may be priming the brain for dementia. Sleeping pills, a common remedy, may only make matters worse, as they may interfere with our natural bodily rhythms. Indeed, the long-term use of some sleeping pills has been tied to an increased risk of Alzheimer’s disease.
Experts generally recommend cognitive behavioral therapy, or CBT, which teaches people to challenge negative thoughts at bedtime with positive thoughts that induce relaxation, as the first-line treatment for sleep problems.
Other recommendations include avoiding coffee and other caffeine-rich beverages at least 10 hours before bedtime, and not drinking alcohol in the evening hours. Avoid phones and computers tablets near bedtime, since the light they emit can interfere with circadian rhythms. In addition, make the bed a sleep sanctuary, rather than a place to watch TV. Until more effective treatments or a cure for Alzheimer’s disease are found, getting better quality sleep may be one more way to help slow the onset of dementia as the years advance.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Rui Liu, MD; Yifei Ren MD; Tingting Hou, MD, PhD; et al: “Associations of sleep timing and time in bed with dementia and cognitive decline among Chinese older adults: A cohort study.” Journal of the American Geriatrics Society, September 21, 2022