[The epidemiological transition during the 20th century].
An epidemiological transition took place during the 20th century causing profound demographic changes in the industrialised world. The transition is a reflection of lower birth rates and changing disease rates. These changes are associated with improved nutrition, hygiene and other social factors, and are unevenly distributed according to socio-economic status. Preventive efforts, intentional or not, and diagnostic and therapeutic improvements will contribute to a demographic transition resulting in an increasing number of elderly people. The epidemiological transition and the development of more sophisticated medical techniques will increase the demand for health care.