RESUMEN
BACKGROUND: The purpose was to examine whether longitudinal changes in self-reported energy predict incident mobility disability and mortality. We further explored whether changes in energy-related behaviors (physical activity, appetite, or sleep quality) would explain these associations. METHODS: N = 2021 participants from the Health, Aging and Body Composition Study free from mobility disability and with at least three energy assessments from years 2 to 10. MEASUREMENTS: The outcomes were time to first self-reported inability to walk a quarter of a mile (mobility disability) and death. Self-reported energy level (SEL) was a single-item indicator over the prior month, ranging from 0 to 10; person-specific slopes measured whether individuals increased or decreased in SEL across the total follow-up time (mean 7.09 years, +1.72, range 2-8 years). Potential energy-related mediators were baseline and change in self-reported physical activity, appetite, and sleep quality. Covariates were baseline levels and change in demographics, health characteristics and behaviors, tiredness, cognition, mood, and gait speed. RESULTS: A total of 947 developed disability and 567 died over the study follow-up. A one-point change in SEL over the follow-up (or an average 0.125 points/year) was inversely associated with a 35% risk of incident mobility disability (hazard ratio = 0.65, 95% confidence interval [CI] = 0.55, 0.76, p < 0.001) and 33% risk of death (hazard ratio = 0.67, 95% CI = 0.42, 0.87, p = 0.003), independent of covariates. Potential energy-related mediators did not attenuate this association. CONCLUSIONS: In this longitudinal analysis of community-dwelling older adults, energy decline was common and a significant independent predictor of disability risk and mortality.