Intrinsic capacity differs from functional ability in predicting 10-year mortality and biological features in healthy aging: results from the I-Lan longitudinal aging study

This study aimed to explore the biological features and mortality risk of intrinsic capacity (IC) and functional ability (FA). Based on data from 1839 participants from the I-Lan Longitudinal Aging Study, multivariable Cox proportional hazard models were used to evaluate the predictive ability of IC (range 0–100) and FA (range 0–100) on 10-year mortality. Of 2038 repeated measurements for IC within a 7-year observational period, multivariable logistic regression was used to compare biological features of participants with maintained, improved and rapidly deteriorated IC. A 1-point increased IC value was associated with a 5% (HR 0.95, 95% CI 0.93–0.97, p < 0.001) decrease in mortality risk. Low IC (HR 1.94, 95% CI 1.39–2.70, p < 0.001) was associated with higher mortality risk. Hyperglycemia (OR 1.40, 95% CI 1.09–1.81, p = 0.010), low serum levels of DHEA-S (OR 3.33, 95% CI 1.32–8.41, p = 0.011), and high serum levels of C-reactive protein (OR 1.45, 95% CI 1.05–2.00, p = 0.023) were associated with low IC at baseline. Low serum levels of DHEA-S (middle tertile OR 1.84, 95% CI 1.15–2.95, p = 0.012; lowest tertile OR 2.25, 95% CI 1.34–3.77, p = 0.002) and vitamin D deficiency (OR 1.82, 95% CI 1.02–3.27, p = 0.044) were associated with rapid deterioration of IC. IC and FA predicted 10-year mortality, whereas chronic inflammation, hyperglycemia, and low DHEA-S were associated with low IC status. Low DHEA-S and vitamin D deficiency may be considered as potential biomarkers of rapid IC declines, which implies underlying biological mechanisms of healthy aging.