Burden of disease--implications for future research.

One overall challenge for public health and medicine in the future is to allocate available resources effectively to reduce major causes of disease burden globally and to decrease health disparities between poor and affluent populations. The major risk factors for death and disability worldwide are malnutrition; poor water supply, sanitation, and personal and domestic hygiene; unsafe sexual behavior; tobacco use; alcohol use; occupational hazards; hypertension; physical inactivity; illicit drugs; and air pollution. The challenge for research in the 21st century is to maintain and improve life expectancy and the quality of life that was achieved for most of the world's population during the 20th century.