The view from the top: Centenarians and global health

Over the past several decades, life expectancy has gradually increased throughout the world, and in some countries, such as Japan, the average life expectancy is now more than 80 years. Nevertheless, only about one to two persons per 10,000 will live to be one hundred years. Persons now aged 100 or more, were born on or before 1912, at a time when normal life expectancy was about 50 years. Thus centenarians are an example of a group that has successfully evaded the usual forces of mortality that affect all other humans. What can we learn from these remarkable, highly selected individuals, and what are the implications for global health?Exceptional individuals have had long lives in earlier times[1]. Hippocrates, considered to be the father of medicine, may have been a centenarian.Indeed, even in the late middle ages and early Renaissance, if one survived childbirth and the numerous, often fatal diseases of young adulthood, there was a reasonable chance of living into the seventies or eighties [2,3]. These reports imply that even in periods when the overall mortality was high, some individuals lived to what would at the time have been considered exceptional ages.From a global viewpoint, the burden of disease is determined by two factors: life expectancy and the proportion of healthy years of life expectancy—the healthy span. By studying centenarians we can learn a great deal about disease (or absence of disease) at the extreme end of life, and we can use this information to assess what health services we will be required to provide as the world’s population gradually ages. The aim of this review is to summarize the factors that might be related to extreme longevity, and to discuss the global implications of increasing life span.