Abstract
Background:
Slower gait speed is associated with adverse outcomes of aging, such as falls and mortality. We hypothesized that physical inactivity, which is prevalent in the elderly, is a major risk factor for slowed gait speed independent of white matter hyperintensity volume (WMHV) and silent brain infarcts (SBI) on magnetic resonance imaging (MRI).
Methods:
In the Northern Manhattan MRI sub-study (n = 1290), 702 participants had physical performance measures a mean of 5 years after initial MRI. Assessment of gait speed was via a timed 5 meter walk test, averaged over 3 trials. Physical inactivity was assessed using a validated questionnaire at initial enrollment. Multi-variable linear and logistic regression models were fit to examine the association between physical inactivity and gait speed as a continuous outcome and binary outcome cut off at the lowest quartile. Models were adjusted for sociodemographics, hypertension, diabetes, waist circumference, osteoarthritis, and grip. Further mediation analyses were performed adjusted for WMHV and SBI.
Results:
The mean age at gait assessment was 74(±8.5) years, 61% women and 70% Hispanic; mean gait speed was 1.0±0.3 meter/second. In multi-variable models physical inactivity (54% of cohort), compared to physically activity, was associated with mean 0.04 m/s slower gait speed (p=0.03), and a greater odds of gait speed <0.85 m/s (lowest quartile)(adjusted OR=1.69, p-value=0.02). SBI (beta = -0.05, p= 0.04) and WMHV (beta = -0.02 per SD, p=0.02) were independently associated with gait speed. The association between physical inactivity and gait speed was unchanged after adjusting for WMHV and SBI.
Conclusion:
Physical inactivity is associated with slower gait speed independently of osteoarthritis, markers of sarcopenia, and subclinical ischemic brain injury. Modifying sedentary behavior poses a target for interventions aimed at reducing physical aging.