H. Hafner, G. Moschel, N. Sartorius The size of the world's population aged over 65 was estimated at about 250 million in 1980; by the year 2025 it is expected to grow to about 760 million (see Hauser, this volume). This sharp increase in life expectancy at birth, in some countries amounting to almost 100% in only a hundred years, has resulted from better nutrition and improved living conditions, hygiene and medical care. Not only life expectancy at birth, but also further life expectancy in advanced age has shown a clear, though more moderate increase. This increased life expectancy,...