Validation of the Construct of Intrinsic Capacity in a Longitudinal Chinese Cohort

Objectives We examined the structure and predictive ability of intrinsic capacity in a cohort of Chinese older adults. Methods We used data from the MrOS and MsOS (Hong Kong) study, which was designed to examine the determinants of osteoporotic fractures and health in older Chinese adults. We analysed baseline and the 7-year follow-up data using exploratory factor analysis, confirmatory factor analysis (CFA), and mediation analysis. Results The study consisted of 3736 participants at baseline (mean 72.2 years), with 1475 in the 7-year follow-up. Bi-factor CFA revealed five sub-factors labelled as 'cognitive', 'locomotor', 'vitality', 'sensory', and 'psychological' and one general factor labelled as 'intrinsic capacity'. The model fits the data well, with Root Mean Square Error of Approximation (RMSEA)=0.055 (90% CI=0.053-0.058) for the 5-factor model and RMSEA=0.031 (90% CI=0.028-0.035) for the bi-factor model. Significantly lower intrinsic capacity scores were found in older age groups, women, as well as those who had lower levels of education, lower subjective social status, reported more chronic diseases, or a higher number of IADL limitations (All p<0.0001). Intrinsic capacity had a direct effect in predicting incident IADL limitations at the 7-year follow-up (beta=-0.21, p<0.001). The effect was larger than the direct effect of the number of chronic diseases on incident IADL limitations (beta=0.05, not significant). Conclusions This study supports the construct and predictive validity of the proposed capacity domains of intrinsic capacity. The findings could inform the development of an intrinsic capacity score that would facilitate implementation of the concept of intrinsic capacity in clinical practice.