Intrinsic capacity across the adult lifespan in China: baseline analysis from the nationwide longitudinal PENG ZU cohort

Intrinsic capacity (IC), a composite measure of physical and mental capacities, reflects the functional manifestations of biological aging, yet large-scale population evidence on how IC varies throughout adulthood outside Western settings remains limited. Using data from 17,086 Chinese adults aged 25-89 years in the nationally representative PENG ZU cohort, we characterized age-related variation in IC and its associated factors. IC was assessed across five domains (locomotion, cognition, vitality, psychological, sensory) using self-reported data and physical performance tests. A composite IC score was generated using weighted domain scores and standardized to a 0-100 range. IC levels declined progressively with age, with a sharper decrease and greater variability observed after age 60 in both sexes. The mean IC score was 67.8 (SD = 14) for participants aged < 60 years and 48.6 (SD = 17) for those aged ≥ 60 years. Inflection points were identified at age 60 for men and 62 for women, with significantly faster decline thereafter. The coefficient of variation in IC scores increased with age and differed significantly between adjacent age groups after 60 years. Among those aged ≥ 60, only 6.0% retained high IC, whereas nearly one-third experienced moderate-to-severe loss. Locomotion, cognition, vitality, and sensory domains showed marked age-related decline, with the largest reductions in cognition (60.7%), followed by locomotion (52.9%), vitality (51.0%), and sensory function (39.5%) between ages 50-54 and 85-89, while the psychological domain remained stable. Multivariate ANOVA identified age, education, and health consciousness (assessed via self-reported beliefs about personal responsibility for maintaining health) as the top factors associated with IC. Older age was associated with lower IC, whereas higher education and greater health consciousness were associated with higher IC. Furthermore, health consciousness was inversely associated with ADL/IADL disability across all age groups. These findings identify around 60 years as a critical window for the preservation of intrinsic capacity in Chinese adults and highlight health consciousness as a promising modifiable correlate that merits further investigation in the context of healthy aging.