To determine the functional age of an individual, a quantitative system for the assessment of aging status was developed in the present study. A total of 1579 subjects were selected randomly from patients undergoing physical examination. The index of organic mild impairment (IOMI) and IOMI corrected for age (COMI) were calculated. By receiver operating characteristic (ROC) curve analysis of the IOMIs of younger and elderly subjects, a cutoff value for COMI of 30% was obtained. About 95% of <30-year-old subjects were healthy. These data suggest that organs and systems reflect the aging status of an individual and may be a useful tool for evaluating health status.