<p><b><i>Introduction:</i></b> Gait speed is associated with multiple
adverse outcomes of aging. We hypothesized that physical inactivity
would be prospectively inversely associated with gait speed
independently of white matter hyperintensity volume and silent brain
infarcts on MRI. <b><i>Methods:</i></b> Participants in the Northern
Manhattan Study MRI sub-study had physical activity assessed when they
were enrolled into the study. A mean of 5 years after the MRI,
participants had gait speed measured via a timed 5-meter walk test.
Physical inactivity was defined as reporting no leisure-time physical
activity. Multi-variable logistic and quantile regression was performed
to examine the associations between physical inactivity and future gait
speed adjusted for confounders. <b><i>Results:</i></b> Among 711
participants with MRI and gait speed measures (62% women, 71% Hispanic,
mean age 74.1 ± 8.4), the mean gait speed was 1.02 ± 0.26 m/s. Physical
inactivity was associated with a greater odds of gait speed in the
lowest quartile (<0.85 m/s, adjusted OR 1.90, 95% CI 1.17-3.08), and
in quantile regression with 0.06 m/s slower gait speed at the lowest 20
percentile (<i>p</i> = 0.005). <b><i>Conclusions:</i></b> Physical
inactivity is associated with slower gait speed independently of
osteoarthritis, grip strength, and subclinical ischemic brain injury.
Modifying sedentary behavior poses a target for interventions aimed at
reducing decline in mobility.</p
