Subjective Health and Physical-Activity Engagement across Adulthood: Distinguishing between Within-Person and Between-Person Associations

Introduction: It is assumed that age-related increases in loss (e.g., health decline) motivate behavioral changes (e.g., prevention of health decline) across adulthood. This assumption has rarely been directly tested in empirical research, and the current study seeks to fill this gap. Methods: By performing random intercept cross-lagged panel model and multilevel modeling analyses on a three-wave longitudinal dataset from the Midlife in the United States survey (N = 7,108; 51.6% female; between 20 and 75 years at T1), we examined the between-person and the within-person associations between subjective health and engagement in physical activity. Chronic conditions, difficulty in performing daily activities, and demographic variables were controlled for. Results: At the between-person level, subjective (i.e., self-rated) health was positively associated with physical activity in the whole sample and the older subgroup (T1 age >55 years), but not in the younger subgroup (T1 age <35 years). At the within-person level, the association between subjective health and subsequent physical activity was negative in the whole sample and the older subgroup, but nonsignificant (between T1 and T2) or positive (between T2 and T3) in the younger subgroup. Discussion: This study revealed various associations between subjective health and engagement in physical activity across levels (the within- vs. between-person level) and across age groups (younger vs. older group). The finding contributes to a better understanding of people's health behavior in reaction to health decline at different ages. It also supports the proposition that age-related intraindividual increases in losses (e.g., health decline) motivate behaviors that counteract such losses (e.g., physical activity that protects health).