# Rest‐Activity Rhythms and Cognition in Older Adults With and Without Insomnia

## TL;DR

This study found that disrupted rest-activity rhythms in older adults with insomnia are linked to better attention performance, but no overall cognitive differences between groups.

## Contribution

The study introduces a novel focus on rest-activity rhythms as a potential mediator of cognitive performance in insomnia.

## Key findings

- Older adults with insomnia showed reduced rest-activity rhythm amplitude and more activity during rest periods.
- Better attention was associated with stronger rest-activity rhythms and less fragmentation, regardless of insomnia status.
- No cognitive differences were found between insomnia and non-insomnia groups.

## Abstract

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.