Until now, gerontologists have maintained the notion of a Fixed, unchangeable, maximum life span. However, recent historic-demographic research has shown that the highest age attained has increased by several years since the beginning of this century. Most studies on the inheritance of longevity have shown a small to moderate genetic influence. But the frequency of several risk genes are not lower in centenarians except for the e4-allele of the APOE-genotype. Although certain gene-environment interactions may be of greater importance, it is more likely that environmental factors late in life play the most important part. This is supported by demographic studies which indicate that the dramatic increase in the proportion of centenarians is mainly due to periodical effects related to the drastic fall in mortality among the elderly. The reasons must therefore be found in conditions which have either postponed the appearance of fatal diseases or slowed down the mortality of such diseases, such as improvement of the living conditions, life styles, health care and treatment of the elderly. Certain personality traits and special strategies for coping have been found to be more prevalent in centenarians than in younger elderly and these may also be important in surviving health-threatening conditions. However, the fact that centenarians are survivors does not mean that they are still healthy. In the most representative studies, a high prevalence of a number of diseases and a considerable comorbidity, especially with regard to arteriosclerosis, heart failure, hypertension, dementia, and osteoarthrosis are;found, and many centenarians have survived major diseases thanks to medical treatment and surgery. It is, however, possible that the comorbidity is less serious and that a few, specific diseases are less frequent than in younger elderly. Furthermore, a number of basic biological mechanisms seems to be well-preserved in several centenarians. Finally, it also should be stressed that at least one third of the centenarians are cognitively intact, and that a smaller proportion may even be considered to be relatively autonomous, still looking forward to their next birthday. It may be expected that this proportion will increase in the future as will the life-expectancy of centenarians. Longevity may thus be perceived as part of our postmodern condition with its mix of pleasure and suffering.
