Abstract
OBJECTIVES: To examine the association between stopping to rest during a 400-m usual-pace walk test (400-MWT) and incident mobility disability in older persons with functional limitations. DESIGN: Prospective cohort study. SETTING: Community based. PARTICIPANTS: Four hundred twenty-four participants in the Lifestyle Intervention and Independence for Elders Pilot (LIFE-P) Study aged 70 to 89 with functional limitations (summary score < or =9 on the Short Physical Performance Battery (SPPB)) but able to complete the 400-MWT within 15 minutes. MEASUREMENTS: Rest stops during the 400-MWT were recorded. The onset of mobility disability, defined as being unable to complete the 400-MWT or taking more than 15 minutes to do so, was recorded at Months 6 and 12. RESULTS: Fifty-four (12.7%) participants rested during the 400-MWT at baseline, of whom 37.7% experienced mobility disability during follow-up, versus 8.6% of those not stopping to rest. Performing any rest stop was strongly associated with incident mobility disability at follow-up (odds ratio (OR)=5.4, 95% confidence interval (CI)=2.7-10.9) after adjustment for age, sex, and clinic site. This association was weaker, but remained statistically significant, after further adjusting for SPPB and time to complete the 400-MWT simultaneously (OR=2.6, 95% CI=1.2-5.9). CONCLUSION: Stopping to rest during the 400-MWT is strongly associated with incident mobility disability in nondisabled older persons with functional limitations. Given the prognostic value, rest stops should be recorded as part of the standard assessment protocol for the 400-MWT.