Concepts and Theories of Longevity

This chapter is concerned with the concepts, statistics, theories, and future levels of human longevity, particularly extreme longevity. The term, extreme longevity or superlongevity, is used here to refer to centenarians, that is, persons with a verified age of 100 years or more. Among these we identify for special attention a subgroup known as supercentenarians, that is, persons with a verified age of 110 years or more. In both popular and scientific reporting, people aged 85 years and over have often been considered as extreme aged, but the rapid increase in the number of people in these older age groups suggests a redefinition of the notion of extreme aged. Persons in the broad age group 85 years and over are also referred to as persons of advanced age and the oldest-old. The former description now seems appropriate but the latter one does not. Preferences vary among demographers and gerontologists as to the choice of designations for these groups.