Physical Independence and Mortality at the Extreme Limit of Life Span: Supercentenarians Study in Japan

Background. Prevention of disability is a major challenge in aging populations; however, the extent to which physical independence can be maintained toward the limit of human life span remains to be determined. Methods. We examined the health and functional status of 642 centenarians: 207 younger centenarians (age: 100-104 years), 351 semi-supercentenarians (age: 105-109 years), and 84 supercentenarians (age: >110 years). All-cause mortality was followed by means of an annual telephone or mailed survey. Results. Age-specific disability patterns revealed that the older the age group, the higher the proportion of those manifesting independence in activities of daily living at any given age of entry. Multiple logistic regression analysis identified male gender and better cognitive function as consistent determinants of physical independence across all age categories. In a longitudinal analysis, better physical function was significantly associated with survival advantage until the age of 110. However, mortality beyond that age was predicted neither by functional status nor biomedical measurements, indicating alternative trajectories of mortality at the highest ages. Conclusions. These findings suggest that maintaining physical independence is a key feature of survival into extreme old age. Future studies illuminating genetic and environmental underpinnings of supercentenarians' phenotypes will provide invaluable opportunities not only to improve preventive strategies but also to test the central hypotheses of human aging.