Regular Research ArticleA Change in Sleep Pattern May Predict Alzheimer Disease
Introduction
Approximately 50% of older adults report problems regarding their sleep,1 and sleep problems may be particularly common in a variety of clinical health settings older adults may be more likely to encounter, including hospice2 and assisted living facilities.3 Sleep problems are likely to increase with age4, 5, 6 and may adversely affect overall well-being.7 Two separate cross-sectional studies found that self-reported sleep quality was associated with poorer cognitive performance8 and that reporting reduction in sleep duration may be associated with poorer global cognitive status.9 A change in sleep pattern (shorter or greater sleep duration) was also associated with worse memory10 and greater cognitive decline.11 Finally, insomnia accelerated cognitive decline over 3 years of follow-up, although only in men and not in women.12
Sleep disturbances were also identified as a potentially important area in research on risk factors for dementia.13 This was partially based on evidence that more sleep disruptions (e.g., insomnia, restless legs) were associated with increased risk of vascular dementia after 10 years.14 However, the contribution of sleep problems to the risk of dementia is still poorly understood.
There is also evidence that reduced duration and/or quality of sleep may adversely affect brain health specifically, likely via weakened neuronal structures, increased risk of cell death, and via cardiovascular pathways. Middle-aged adults who average 5 hours of sleep per night are more likely to have hypertension than those averaging 7 hours.15 Also, having poor sleep quality may increase the risk of stroke and raise blood pressure.16, 17 Together, these findings may point to a potential cardiovascular pathway toward poor brain health.18, 19
Sleep may also be associated with increased dementia risk because of its interplay with psychological stress. Insomnia is one of the diagnostic criteria for Major Depressive Episode and Major Depressive Disorder,20 and sleep problems have been identified as a possible risk factor for subsequent depression.21, 22 Depressive symptoms may therefore be an important variable in any association between sleep problems and dementia.
We examined whether a subjective report of change (reduced duration and/or depth) in sleep pattern was associated with an increased risk of incident all-cause dementia and Alzheimer disease (AD). In addition, we tested whether an association between change in sleep pattern and dementia may be explained by vascular health and/or depressive symptoms. We also considered the influence of demographic factors, lifestyle factors, apolipoprotein E epsilon 4 allele (apoE ε4), and the potential modification effect of sleeping pills. Finally, we examined change in sleep pattern categorized in three groups and introduced into the model as a continuous variable to test for a potential dose–response association.
Section snippets
Sample
We used data from the population-based Kungsholmen Project, a longitudinal study of aging and dementia among adults aged 75 years and older residing in Kungsholmen district, Stockholm, Sweden. Data collection included a baseline and four follow-up examinations.23, 24 Individuals living in Kungsholmen born before 1913 were invited to participate in the initial measurement, which took place from 1987 to 1989. Follow-up data collections occurred approximately every 3 years until 2000 for a total
Results
The sample is described in Table 1. Participants were predominantly women, living alone, alcohol consumers, nonsmokers, and did not engage in physical activity. Approximately one-fourth of the participants had symptoms of depression or needed assistance with at least one activity of daily living. Most reported experiencing pain. Those reporting change in sleep pattern were significantly more likely to be women, to have depressive symptoms, and to take sleeping pills than participants reporting
Discussion
We examined self-reported change (reduced duration and/or depth) in sleep pattern in relation to incident all-cause dementia and AD in a sample of adults aged 75 years and older. After 9 years of follow-up, we found that moderate or severe change (sleep reduced in length by at least 2 hours compared with previous norm) was associated with an increased risk of incident dementia, particularly AD. The results provide additional evidence that disruptions to sleep may be associated with an increased
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