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Associations of 24-hour Light Exposure and Activity Patterns and Risk of Cognitive Impairment and Decline in Older Men: The MrOS Sleep Study.



Older men with worse alignment of activity and light may have lower levels of cognition and increased rates of cognitive decline.


This cohort consisted of 1,036 older men (81.1 ± 4.6 years) from the MrOS Sleep Study (2009-2012). Light and activity levels were gathered by wrist actigraphy. Phasor analysis was used to quantify alignment of light-dark and rest-activity patterns (magnitude) and their temporal relationship (angle). Global cognitive function (Modified Mini-Mental State examination, 3MS) and executive function (Trails B test) were measured, then repeated 4.2 ± 0.8 years later. Linear regression models examined the associations of phasor magnitude and angle with cognition and cognitive decline. Models were adjusted for age, clinic, race, education and season.


Smaller phasor magnitude (worse aligned light and activity patterns) was associated with lower initial level and increased decline in executive function. Compared to those with higher phasor magnitude, those with lower magnitude took an average of 11.1 seconds longer to complete the Trails B test (Quartile 1 vs. Quartile 4, p=.02). After follow-up, Trails B completion time increased an average of 5.5 seconds per standard deviation increase in phasor magnitude (95% CI 0.7-10.4, p=.03). There were no associations with phasor angle, and none with magnitude and global cognition (3MS).


Among older men, worse alignment of light and activity patterns was associated with worse initial performance and increased decline in executive function, but not related to global cognition. Interventions that improve alignment of light and activity may slow cognitive decline in older adults.

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