Functional correlates of self-reported energy levels in the Health, Aging and Body Composition Study

Background: Effects of fatigue on health in older age are well studied, yet little is known about the clinical relevance of energy perception. Aims: To explore cross-sectional associations of self-reported energy with physical and mental health metrics in the Health, Aging, and Body Composition Study. Methods: Participants rated their energy from 0 to 10; the outcome was energy dichotomized at the median (≥ 7 = higher energy). Four domains were assessed: depressive symptoms (Center for Epidemiologic Studies Depression Scale); physical performance (function: usual and rapid gait speed; fitness: 400-m walk time); physical activity (casual walking, walking for exercise, and intense exercise); and cognitive function (Modified Mini-Mental State Examination and Digit Symbol Substitution Test). Covariates bivariately associated with energy entered a multivariable logistic regression model, adjusted for demographics, chronic conditions, and strength. Results: Depressive symptoms, physical performance and activity, but not cognition, were bivariately associated with energy (p < 0.0005). Younger age, male sex, greater strength, and absence of chronic conditions predicted higher energy (p < 0.001). In a multivariable model, depressive symptoms [adjusted odds ratio (aOR) 95% CI 0.69 (0.62, 0.76)] and 400-m walk times [aOR = 0.81 (0.72, 0.91)] were inversely associated with energy; usual and rapid gait speed [aOR = 1.3 (1.2, 1.4); aOR = 1.2 (1.1–1.4)], and time spent in intense exercise [aOR = 1.4 (1.1–1.7)] were positively associated with energy. Discussion: In this cohort with a range of chronic conditions and fatigue, perceiving higher energy levels may reflect better emotional and physical health. Conclusion: Energy should be considered in multidimensional clinical assessments of older age.