Functional status of centenarians in Tokyo, Japan: Developing better phenotypes of exceptional longevity

Background. Centenarians are sometimes said to be representative of lifelong healthy aging. Whether they are, in fact, examples of healthy aging remains a subject of debate. The existence of heterogeneity in functional status has been reported repeatedly in previous studies of centenarians. However, there is as yet no standardized classification system with which to describe their functional phenotype. Methods. As part of a dynamic cohort study, we studied 304 centenarians (65 men and 239 women) living in Tokyo. Their functional status (sensory, physical, and cognitive), which we used to represent their phenotype, was assessed and subsequently classified by standard assessment methods (simple questionnaire, Barthel index, Mini-Mental State Examination, and the Clinical Dementia Rating, respectively). Results. We classified participants into 4 categories according to their functional status. Only 5 (2%) were classified as "Exceptional," with all of their functions graded as excellent, and 56 (18%) were "Normal," exhibiting maintenance of fine cognitive and physical functions. One hundred sixty-seven (55%) were "Frail," exhibiting impairment of either cognitive or physical functions, and the remaining 76 (25%) were "Fragile," exhibiting deterioration of both physical and cognitive functions. Conclusions. The relationships between biochemical marker, mortality rates, lifestyle, and functional phenotypes demonstrated by this classification method indicate that the system is reliable to address the functional status of extremely old persons. Thus, this framework would be a useful tool for exploring the factors that contribute to exceptional longevity as well as those that help to maintain the functional status of the extremely old population.