Clinical research on extreme longevity: The FACET experience.

People with extreme longevity represent a unique model to study the biology of aging. Unfortunately, their inclusion in research projects is challenging with the consequent lack of evidence and the need to rely on small convenience samples. Given the growing global aging population, especially in the segment of the oldest old (i.e., aged 90 and older), research in this population has become crucial. Furthermore, by studying the characteristics of extremely longeval persons, it might be possible to 1) better understand the mechanisms of aging, and 2) identify endogenous or exogenous factors contributing to a long life. The design and implementation of research activities in the oldest people need special consideration and a pragmatic approach. Possible implementable solutions and suggestions are provided from experience gained during the conduction of the FAtigue in CEnTenarians (FACET) study.