The prognostic value of repeated measures of lower extremity performance: should we measure more than once?

BACKGROUND Lower extremity physical performance measured at one point in time is a powerful predictor of future disability. Whether information on previous lower extremity performance adds independent information to disability prediction compared to a single measure alone is unknown. METHODS Data are from community-dwelling men and women aged greater than or equal to 65 years enrolled in the Invecchiare in Chianti study who were free of mobility and activities of daily living (ADL) disability at baseline and at 3-year follow-up (n = 891). Walking speed and Short Physical Performance Battery were examined at baseline and at the 3-year follow-up (zero-time). Logistic regression analysis was used to examine the associations between physical performance measures and incident mobility and ADL disability detected at the 6-year and 9-year follow-up. RESULTS Walking speed and Short Physical Performance Battery score assessed at the zero-time strongly predicted development of mobility and ADL disability during the subsequent 6 years independent of walking speed/Short Physical Performance Battery score 3 years prior. CONCLUSIONS Current lower extremity performance is a strong risk factor for subsequent mobility and ADL disability and is independent of performance 3 years prior, which has negligible independent prognostic value.