Multidimensional predictors of physical frailty in older people: identifying how and for whom they exert their effects.

Physical frailty in older people is an escalating health and social challenge. We investigate its physical, psychological, and social predictors, including how and for whom these conditions exert their effects. For 4638 respondents aged 65-89 years from wave 2 of the English Longitudinal Study of Ageing, we examine prediction of future physical frailty by physical, psychological, and social conditions using latent growth curve analysis with multiple indicators. In addition, we explore their indirect effects through disease and physiologic decline, and repeat these analyses after stratification by gender, age group, and selected conditions which are possible moderators. We find that chronic disease, allostatic load, low physical activity, depressive symptoms, cognitive impairment, and poor social support all predict future physical frailty. Furthermore, chronic disease and allostatic load mediate the effects of low physical activity, depressive symptoms, and cognitive impairment on future physical frailty. Finally, although poor social integration is not a predictor of future physical frailty, this condition moderates the indirect effect of poor social support through chronic disease by rendering it stronger. By virtue of their roles as predictor, mediator, or moderator on pathways to physical frailty, chronic disease, allostatic load, low physical activity, cognitive impairment, depressive symptoms, poor social support, and poor social integration are potentially modifiable target conditions for population-level health and social interventions to reduce future physical frailty in older people.