Rest-Activity Rhythms and Cognition in Older Adults With and Without Insomnia

Insomnia is associated with risk for cognitive deficits. However, the literature assessing cognitive impairments in insomnia is replete with conflicting findings; it is unclear whether individuals with insomnia exhibit impaired cognition or whether specific sleep features consistently predict cognitive performance in insomnia. Disturbance in rest-activity rhythms may be more directly associated with cognitive deficits in insomnia. In a sample of older adults with (n = 30) and without insomnia (n = 33), we examined (1) whether insomnia diagnosis was associated with differences in rest-activity rhythms and cognition, and (2) whether rest-activity rhythms were associated with cognition across domains. We used a remote comprehensive cognitive battery to test four domains of cognition: attention, inhibition, cognitive flexibility, and episodic memory. Compared to older adults without insomnia, older adults with insomnia exhibited attenuated rest-activity rhythms, indicated by lower relative amplitude (F _1,59 = 6.96, p = 0.01) with greater activity during the rest period (F _1,59 = 7.96, p = 0.01). No group differences were found in cognition. Better attention performance was associated with greater amplitude (relative amplitude: β = -0.38, p = 0.02; amplitude: β = -0.45, p = 0.01), activity (M10: β = -0.38, p = 0.01) and less fragmentation of rest-activity rhythms (intradaily variability: β = 0.34, p = 0.03), irrespective of insomnia diagnosis. No other cognitive domains were associated with rest-activity rhythms. Future studies should develop and test interventions to improve rest-activity rhythms and cognitive outcomes in older adults with and without insomnia.