Seasonal trends in US asthma hospitalizations and mortality

Illness, hospitalization, and death from asthma occur with a seasonal periodicity, but no large-scale study of these seasonal effects has been described. To gain insight into these aspects of asthma, two large databases, the US Vital Records and the National Hospital Discharge Survey, were examined for the period between January 1, 1982, and December 31, 1986. Results showed a principal discharge diagnosis of asthma for approximately 458,000 hospitalizations, with the highest hospitalization rates for children under five years and adults older than 65. Nonwhites were hospitalized almost three times as often as whites. The annual average mortality was 1.52 per 100,000 population, with an overall increase of 25 percent during the period analyzed. Mortality for nonwhites was almost twice that for whites. Monthly mortality evaluation showed striking seasonal trends. Periods throughout the year differed by as much as 25 percent, with the peak mortality occurring during January and the lowest point in September. The youngest group (age 5 through 34) had its lowest death rate in February and its highest in July. The oldest age group (65 or above) had its highest mortality between January and March and its lowest between July and September, a pattern similar to that for the whole group. The middle-aged group showed no particular seasonal pattern. Hospitalizations, too, showed patterns: the number decreased from June through September, then increased beginning in September. Among older patients, there was a close seasonal match between rates of death and hospitalization, while for younger people, hospitalizations peaked in the fall, mortality in summer. More people in this group died in a hospital in the autumn, while during the summer, out-of-hospital deaths or deaths upon arrival were more common. These results must be interpreted with due regard for several other factors besides asthma-related ones that could have influenced the data, but, on the whole, they indicate that the seasonal variations in hospitalization and death rate due to this condition could have implications for its etiology and treatment. (Consumer Summary produced by Reliance Medical Information, Inc.)