Globally, adults are now surviving longer, largely because during the past half century, when they were children, epidemics of infectious diseases such as tuberculosis and respiratory disease were being better controlled. The continuing gains in the survival of infants and young children means that the adult population is increasing.
- Currently, just over half the population is of working age, 20-64; by 2025 the proportion will have reached 58%.
- The proportion of older people requiring support from adults of working age will have increased from 10.5% in 1955 and 12.3% in 1995 to 17.2% in 2025.
- The health of the adult population of working age will be vitally important if this age group is to support growing numbers of dependants, both young and old.
- However, more than 15 million adults aged 20-64 are dying every year. Most of these deaths are preventable.
- Among the most tragic of these deaths are those of 585 000 young women who die each year in pregnancy or childbirth.
- 2-3 million adults a year are dying of tuberculosis, despite the existence of a strategy that could effectively cure all cases.
- About 1.8 million adults died of AIDS in 1997 and the annual death toll is likely to rise.
The successes achieved in the past 50 years against microbial and parasitic diseases stem from the creation of a healthier environment, with improvements in hygiene and sanitation; treatment with effective and affordable antibiotic and antiparasitic drugs; and the availability of vaccines. Unfortunately, these types of drugs cannot be relied on to the same extent in the future - because of the spread of strains of pneumonia, tuberculosis and malaria that are resistant to the most powerful medicines. Steady increases in cases of and deaths from tuberculosis are evidence of this trend.
- The future of infectious disease control is likely to lie with vaccines rather than drugs.
- In general, noncommunicable diseases such as coronary heart disease, cancer, diabetes and mental disorders are more common than infectious diseases in the industrialized world. Coronary heart disease and stroke have declined as causes of death in these countries in recent decades, while death rates from some cancers have risen.
- In developing countries, as their economies grow, noncommunicable diseases will become more prevalent, largely because of the adoption of "western" lifestyles and their accompanying risk factors - smoking, high-fat diet, lack of exercise. But infectious diseases will still be a major burden, none more so than HIV/AIDS.
- Cancer will remain one of the leading causes of death worldwide. Despite much progress in research, prevention and treatment, only one-third of all cancers can be cured by earlier detection combined with effective treatment. However, many of the remaining cancers could be prevented by a range of measures, including avoiding tobacco use and adopting a healthier diet.
Some likely trends to 2025 are given below:
- Overall, the risk of cancer will continue to increase in developing countries, with stable if not declining rates in industrialized countries. In individual countries, some cancers will become more common, others less common.
- Cases of and deaths from lung cancer and colorectal cancer will increase, largely due to smoking and unhealthy diet. Lung cancer deaths among women will rise in virtually all industrialized countries.
- Stomach cancer will become less common, mainly because of improved food conservation, dietary changes and declining related infection.
- Cervical cancer is expected to decrease further in industrialized countries due to screening; the possible advent of a vaccine would greatly benefit both developed and developing countries.
- Liver cancer will decrease as a consequence of current and future immunization against the hepatitis B virus in many countries and of screening for hepatitis C.
- Diabetes cases in adults will more than double globally, from 143 million in 1997 to 300 million in 2025, largely because of dietary and other lifestyle factors.