OBJECTIVES: To estimate the relationship between 1-year improvement in measures of health and physical function and 8-year survival.
DESIGN: Prospective cohort study.
SETTING: Medicare health maintenance organization and Veterans Affairs primary care programs.
PARTICIPANTS: Persons aged 65 and older (N=439).
MEASUREMENTS: Six measures of health and function assessed at baseline and quarterly over 1 year. Participants were classified as improved at 1 year, transiently improved, or never improved for each measure using a priori definitions of meaningful change: gait speed (usual walking pace over 4 m), 0.1 m/s; Short Physical Performance Battery, 1 point; Medical Outcomes Study 36-item Short Form Health Survey physical function, 10 points; EuroQol, 0.1 point; National Health Interview activity of daily living scale, 2 points; and global health change, two levels or reaching the ceiling. Mortality was ascertained from the National Death Index. Covariates included demographics, comorbidity, cognitive function, and hospitalization.
RESULTS: Of the six measures, only improved gait speed was associated with survival. Mortality after 8 years was 31.6%, 41.2%, and 49.3% for those with improved, transiently improved, and never improved gait speed, respectively. The survival benefit for improvement at 1 year persisted after adjustment for covariates (hazard ratio=0.42, 95% confidence interval=0.29–0.61, P<.001) and was consistent across subgroups based on age, sex, ethnicity, initial gait speed, healthcare system, and hospitalization.
CONCLUSION: Improvement in usual gait speed predicts a substantial reduction in mortality. Because gait speed is easily measured, clinically interpretable, and potentially modifiable, it may be a useful “vital sign” for older adults. Further research is needed to determine whether interventions to improve gait speed affect survival.