Mixed
Fragmentation of the rest-activity rhythm (intradaily variability) is significantly associated with age-related cognitive decline in elderly individuals, independent of age, gender, and cardiovascular risk factors.
For older adults, maintaining a stable daily routine is as important for brain health as sleep duration. Fragmented activity (frequent transitions between rest and activity throughout the day) is linked to poorer cognitive performance. Establishing a consistent, strong circadian rhythm—regular sleep times, regular meal times, and regular daytime activity—may help mitigate age-related cognitive decline, particularly in mental speed and executive function.
Multiple regression analyses showed that the partial correlations of the fragmentation of the sleep-wake rhythm with each of the three cognitive domains (r = -0.16, -0.19, and -0.16 respectively) were significant. These associations were independent from main effects of age, implying that a unique relationship between the rest-activity rhythm and cognitive performance is present in elderly people.
Why this rating
Observational/correlational study with a large sample size (n=144) and rigorous statistical controls, but causality cannot be established.
Source
Fragmentation of the rest‐activity rhythm correlates with age‐related cognitive deficits
Joukje M. Oosterman et al. · Journal of Sleep Research · 2009
DOI 10.1111/j.1365-2869.2008.00704.x
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