Morbidity

September 17, 2011

In general terms, morbidity represents illness—any departure from normal well-being. There is a close relationship between mortality and morbidity, because high levels of morbidity (i.e., an unhealthy population) are associated with high death rates, and vice versa. For example, the life expectancy of women in the united States increased from 49 years at the beginning of the 20th century to 79 years at the beginning of the 21st century. These improvements in longevity are a result of significant changes in the patterns of illness and disease among both women and men, although women have seen a bigger improvement than have men. In fact, in 1900, American women had a life expectancy that was 2 years longer than that of men, and the advantage grew to nearly 8 years by the mid-1970s, before dropping to about 6 years in 2000.

Infectious diseases combined especially with complications of pregnancy have historically been the major sources of morbidity (and, at the extreme, of mortality) among women all over the world. Infectious diseases have been brought under reasonable control by better nutrition that helps people resist disease; clean water and adequate sewage systems that help to prevent the spread of disease; better housing, vaccinations, medical care, and a host of other technological innovations that have spread around the world over the last century. These same changes have also reduced pregnancy-related illness, especially in combination with the dramatic decline in the number of pregnancies and births among women. The rising standard of living and improved status of women have been important motivations for limiting family size, but, of course, the success of this has been heavily dependent upon the availability of a wide range of fertility control measures.

Lower morbidity means that people are healthier into the older ages, at which point degenerative (chronic) diseases tend to become sources of illness, disability, and of course death. Patterns of morbidity vary not only by age and sex, but also regionally across the globe. A useful way of making such comparisons is through the calculation of Disability Adjusted Life Years (DALYs). This concept was introduced by the World Bank in 1990 and has been implemented as the global “burden of disease” studies undertaken by Murray and Lopez at the Harvard School of Public Health, and is now accepted and used widely by the World Health Organization of the United Nations. A DALY is equal to the sum of YLL and YLD, where YLL is equal to the years of life lost due to death at an age earlier than expected, and YLD is the number of years lost to disability as a consequence of injury or illness. If a person could expect to live to age 100 in a perfect world, but dies of a stroke (a type of cardiovascular disease) at age 50, then that person “lost” 50 years of life and the sum of all years of life lost in a society to people dying of stroke would be the YLL for that population in that year. Another person might have had a stroke at age 50, but survived. The severity of the disability with which such a person would have to live would then be given a weight and the number of years of normal functioning lost to the disease would be calculated as the YLD. The total burden of a disease is then the number of years of life that a society loses to a disease through its combined impact on mortality and morbidity.

Among women in the world at the beginning of the 21st century, the greatest number of DALYs lost (i.e., the greatest disease burden) is caused by HIV/AIDS, followed by lower respiratory disease, and unipolar depressive disorders. However, World Bank data show that different diseases are important at different ages among women. At ages 15-44, maternal causes are most important, whereas at ages 45 and older, cerebrovascular diseases cause the greatest morbidity burden.

Regional variations in morbidity are now especially related to HIV/AIDS. In sub-Saharan Africa, there is evidence that migrant labor is a powerful source of the spread of the disease because of the sexual networking that is involved in a subcontinent where the use of the condom has not been as widespread as in other parts of the world. Because HIV/AIDS tends to affect young adults more than other age groups, it places a tremendous burden on a society through the loss of not only family members, but also through dramatically reduced economic productivity. Indeed, in the middle of the 20th century, increases in health care access for workers were pushed by labor unions in Europe and North America on the (correct) grounds that improved health levels of workers would make companies more profitable.

SEE ALSO: Disability, Maternal mortality, Mortality

Suggested Reading

  • Goldman, M. B., & Hatch, M. C. (Eds.). (2000) Women and health. San Diego: Academic Press.
  • Murray, C. J., & Lopez, A. (Eds.). (1996). The global burden of disease: A comprehensive assessment of mortality and disability from diseases, injury, and risk factors in 1990 and projected to 2020. Boston: Harvard University School of Public Health.
  • World Bank. (1993). World development report 1993: Investing in health. New York: Oxford University Press.

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