Demographic and nutritional trends among the elderly in developed and developing regions.

Aging for an individual and aging for a population are related but not the same. For an individual, aging first involves survival to more advanced years, which will inevitably be accompanied by progressive changes in the structure and function of somatic tissues due to a programmed failure of the organism maximally to invest in their maintenance. For a population, aging means an increase in the median age, a dual function of longer survival of individuals and a decrease in fertility. In the wilds of nature, and for all but the recent decades for the human species, survival beyond the peak reproductive years is rare. The hostility of natural selection has its greatest impact on the young and the old. Only captive fowl and beasts, domesticated animal species and Homo sapiens achieve long survival. For humans, life expectancy from birth and from any age thereafter is increasing; median ages of populations and the percentage of persons over 60 y are rising. The affluent developed countries led the way, but developing countries are closing the gap. As of about 1966, a majority of the world's elderly live in developing societies. The rarity of growing old left a dearth of knowledge in the domain of gerontological nutrition, both for lack of motivation to learn and lack of individuals and populations to study. The convening of this workshop signifies that the polarity of interest has shifted 180 degrees. Social, economic, physiological and psychological changes with aging and growing older can both be influenced by diet and influence eating patterns and nutritional status. Many assumptions have been made about these changes, but only recently, with concerted metabolic studies of nutrient requirements in healthy elderly and carefully designed multi-center surveys of the health and nutrition of older segments of populations can a true portrait of the issues be delineated.