A multiple cause-of-death analysis of asthma mortality in the United States, 1990-2001

Objectives . Most analyses of asthma mortality in the United States have relied solely on underlying cause-of-death data, which may underestimate the magnitude of asthma-related mortality. We used multiple cause-of-death data to examine asthma-related mortality trends in the United States. Methods . Data were selected from the United States Multiple Cause-of-Death Files, 1990-2001. Mortality rates and 95% confidence intervals were computed to examine differences in asthma mortality over time and by age, race/ethnicity, and gender. Location of death and seasonal variations in asthma mortality were also assessed, as well as the impact of seasonal respiratory infections. Results . We identified 135,668 asthma-related deaths in the United States over the 12-year period, representing an age-adjusted mortality rate of 4.4 per 100,000. Only 45% of the asthma-related deaths had asthma recorded as the underlying cause. Whites and older adults were less likely to have asthma listed as the underlying cause. Asthma mortality rates mirrored underlying cause trends, increasing slightly between 1990 and 1995, declining between 1996 and 1998, and further declining after International Classification of Disease (ICD)-10 implementation in 1999. Mortality was highest among blacks and the elderly and was higher among females than males. Asthma-related deaths peaked in the winter months and were over four times more likely than non-asthma deaths to have acute upper respiratory infections, influenza, or acute bronchitis listed on the death record. The proportion of asthma-related deaths occurring outside a medical setting increased steadily over the period, from 23.3% in 1990 to 29.4% in 2001. Conclusions . The burden of asthma may be underestimated by relying solely on underlying cause-of-death data. Further research is needed to determine the reasons for the steady increase in out-of-hospital deaths and the continued demographic disparities in mortality.