Relationship of multiple sensory impairments with physical performance in older adults in the Study of Muscle, Mobility and Aging.

Background: Sensory and cognitive function can impact physical performance, but the relationship of multiple sensory impairments (SI) with mobility in older adults is not well understood. We hypothesized that severity and number of SIs would be associated with worse timed physical mobility performance, and that cognitive processing speed would mediate the association.

Methods: Participants (N=832) were older adults (mean age 76.3+/-5.0 years; 59.4% women; 84.2% Non-Hispanic White) who completed tests of physical performance, cognitive function, and multiple sensory domains. Separate linear regression models examined the association of SI with 400m walk, expanded Short Physical Performance Battery (eSPPB), four-square step test (FSST), and stair climb test. Cognitive measures of executive function/processing speed (Digit Symbol Coding (DSC) and Trails Making Test (Trails) B) were tested as potential mediators of the relationship between SI and physical performance.

Results: Each one-point decrement in SI scale was associated with slower 400m walking speed (β=-0.01 m/s, p=0.03), lower eSPPB score (β=-0.05 points, p<0.001), and longer FSST time (β=0.20 seconds, p=0.01), but there was no association with stair climb time. Using a causal mediation approach with DSC and Trails B as potential mediators, 47.9% of the association of SI with 400m walk was mediated, 43.8% of the association of SI with eSPPB, and 56.7% of the association of MSI with FSST.

Conclusions: Greater SIs were associated with worse physical performance in older adults, and the association was partially mediated by measures of cognitive processing speed and executive function. Future studies should investigate the temporal relationship between SI, cognitive and physical function.