Exercise training mitigates the deleterious effects of experimental bed rest on intraindividual variability of executive functioning in older adults: A randomised controlled trial

Abstract

AbstractBackgroundIn older adults, bed rest can occur because of chronic conditions, injury, surgery, or hospitalization. Extreme levels of physical inactivity due to bed rest initiate a downward spiral in several body systems. Exercise is a countermeasure to many of these changes; nonetheless, little is known about the effect of exercise on older adults’ cognition during bed rest. We thus examined the effects of exercise on the intraindividual variability (IIV) of cognitive performance in older adults exposed to 14 days of experimental 6° head‐down bed rest (HDBR) and whether sex moderates its effects. We chose IIV as our outcome measure because it is more sensitive than traditional summary scores of cognitive performance, albeit no studies have explored exercise effects on older adults’ IIV submitted to bed rest.MethodA non‐blinded, parallel‐group, randomised controlled trial. Twenty‐three healthy older adults aged 55‐65 were randomised to: 1) 14 days of HDBR (CON); or 2) 14 days of HDBR with daily aerobic and strength exercise (EX). Data were collected at baseline, HDBR completion, and end of seven‐day‐recovery. The National Institutes of Health Toolbox Cognitive Battery assessed executive function (Flanker Incongruent and Congruent and Dimensional Change Card Sort) and processing speed (Pattern Comparison). IIV was indexed by intraindividual coefficient of variation (ICV) and residual intraindividual standard deviation (R‐ISD), with R‐ISD as our primary measure of interest. Linear mixed models assessed group differences and the moderator role of sex.ResultAt HDBR completion, EX had significantly lower (better) Flanker incongruent ICV (Estimated mean difference = ‐0.10, 95%CI ‐0.19;‐0.003, p = 0.022) and R‐ISD (Estimated mean difference = ‐3.63, 95%CI ‐6.10;‐1.17, p = 0.005) vs. CON. Sex moderated the effect of exercise; females in EX had significantly lower Flanker incongruent ICV vs. CON (Estimated mean difference = ‐0.23; 95%CI ‐0.34;‐0.12, p<0.001). At the end of the seven‐day recovery, EX had significantly lower Flanker incongruent R‐ISD vs. CON (Estimated mean difference = ‐3.11, 95%CI ‐5.70;‐0.052, p = 0.019). Summary scores and processing speed IIV changes were not statistically significant (ps>0.05).ConclusionExercise during HDBR preserved executive functioning, especially in females. Our findings support the delivery of exercises to older adults during bed rest to preserve their cognitive function.