Measuring loss of life, health, and income due to disease and injury: a method for combining morbidity, mortality, and direct medical cost into a single measure of disease impact.

The impact of disease on a population includes illness, death, and medical care cost. Information on all three may be combined in a disease impact scale. The disease impact for a given condition can be defined as the sum of (a) the years of life lost before age 75 per 100,000 population (adjusted to reflect causes of death up to age 100); (b) the person-years of complete disability per 100,000 population, and (c) the direct medical costs in years of average annual personal income per 100,000 population.The sum of (a), (b), and (c)-disease impact in person years per 100,000 population-can be used to compare one disease with another, to estimate the potential effect of programs for risk alteration, and to measure the outcome of planned or accidental changes in society. The data necessary to calculate disease impact are becoming available in many States.In Minnesota, the total disease impact in 1978 was approximately 26,000 person-years per 100,000 population per year. The disease catgories in the International Classification of Diseases, Adapted, Eighth Revision, with the highest disease impact in the State were circulatory diseases (23.7 percent), injury and poisoning (10.9 percent), respiratory system (9.3 percent), neoplasms (9.0 percent); musculoskeletal system and connective tissue (8.8 percent), digestive system diseases (7.5 percent), and nervous system and sense organ diseases (5.8 percent). Circulatory diseases ranked first in morbidity, mortality, and cost, but the rankings for several other categories varied according to the parameter being considered.Use of a disease impact scale such as the one developed in Minnesota avoids dependence on a single parameter such as mortality or cost in making program decisions. In contrast to economic analyses of disease impact, it does not require estimates of discount rates, future rates of inflation, or salaries for homemakers, students, and children. Although the results of present calculations are only approximate, they provide a methodological framework within which correctable deficiencies in data collection methods are readily apparent. The disease impact scale is intended to be a component of a comprehensive disease surveillance system that includes measures of disease impact, the prevalence of risk factors for diseases, and the availability of health resources.