Disentangling the overlap between frailty and intrinsic capacity in older adults

INTRODUCTION: It has been suggested that two prominent frameworks in geriatrics, frailty and intrinsic capacity (IC), represent two opposite ends of the same continuum. Frailty quantifies accumulated deficits and vulnerability, and IC measures an individual's capacities and functional reserves. This study investigates the overlap between frailty and IC in a large cohort of older adults.

METHODS: We analysed 3246 participants aged 55+ from the Longitudinal Ageing Study Amsterdam. Participants were categorised into four groups: neither frail nor low IC, low IC only, frail only, and both frail and low IC. Overlap was examined across age groups. Domain scores (vitality, sensory, cognition, psychology, locomotion) were compared between groups.

RESULTS: Among 57-59 year olds, only 2.2 % were both frail and had low IC. This proportion increased with age, reaching 53.6 % at ages 87-89, while the "frail only" and "low IC only" groups declined. Overlap between frailty and domain scores showed that the "Neither" group consistently had the highest IC scores across all five domains, while the "Both" group consistently had the lowest scores.

CONCLUSIONS: In later life, being frail does not necessarily imply low IC, and vice versa. Frailty and low IC identify different groups in early older age, but the overlap between them becomes more pronounced with increasing age. Comprehensive assessment of ageing therefore requires measures that capture both vulnerability to decline and capacity.