Background: There is a well-known relationship between neurodegenerative disease, disrupted sleep, and cognition. Pathologic and imaging studies have shown that regions in the brain shown to regulate sleep and circadian rhythm are abnormal in Alzheimer disease. Most of these studies have been cross-sectional, and often look at patients already with dementia. This leaves uncertainty with regard to the temporal relationship of circadian disruption and cognitive decline.
Objective: To determine whether disrupted daytime activity and altered sleep patterns predict development of mild cognitive impairment (MCI) or dementia.
Methods: The objective was addressed through the development of a structured, critically-appraised topic. We incorporated a clinical scenario, background information, a structured question, literature search strategy, critical appraisal, results, evidence summary, commentary, and bottom line conclusions. Participants included consultant and resident neurologists, a medical librarian, and behavioral neurology and sleep medicine content experts.
Results: A prospective cohort study of 1282 cognitively normal women demonstrated that when peak circadian activity, as measured by wrist actigraphy, occurred later than average, there was an increased risk of MCI or dementia [odds ratio (OR), 1.83; 95% confidence interval (CI), 1.29-2.61]. Increased odds for dementia or MCI also existed for those with decreased circadian rhythm amplitude (OR, 1.57; 95% CI, 1.09-2.25) and robustness (OR, 1.57; 95% CI, 1.29-2.61).
Conclusions: Disrupted circadian rhythm measures, including lower amplitude, a less robust rhythm, and delayed timing of peak activity on wrist actigraphy, were predictive of future development of MCI or dementia in cognitively normal women.