Increasing Kyphosis Predicts Worsening Mobility in Older Community-Dwelling Women: A Prospective Cohort Study

OBJECTIVES To determine whether increasing kyphosis angle was independently associated with poorer mobility as measured according to the Timed Up and Go Test (TUG), after controlling for other established risk factors. DESIGN Prospective cohort study. SETTING Eleven clinical centers in the United States. PARTICIPANTS Two thousand seven hundred seventy-seven women aged 55 to 80 randomized to the placebo arms of the Fracture Intervention Trial, a randomized controlled trial of the effect of alendronate on risk for osteoporotic fractures. MEASUREMENTS The primary predictor was change in kyphosis angle, measured using the Debrunner Kyphometer; the outcome was change in mobility, measured as performance time on the TUG. Covariates were baseline age, kyphosis angle, body mass index (BMI), self-reported health status, grip strength, change in total hip bond mineral density (BMD), and number of vertebral fractures over a mean of 4.4 years. RESULTS Greater kyphosis angle predicted longer mobility performance times (P <.001), independent of other significant predictors of worsening mobility including age, baseline kyphosis, health status, grip strength, BMI, change in hip BMD, and new vertebral fractures. TUG performance times increased by 0.02 seconds (95% confidence interval (CI)=0.01-0.03) for every 5 degrees increase in kyphosis angle, more than the increase in mobility time of 0.01 seconds (95% CI=0.005-0.03) over 1 year observed in this cohort. CONCLUSION Increasing kyphosis angle is independently associated with worsening mobility. Interventions are needed to prevent or reduce increasing kyphosis and mobility decline.