Background: According to national health statistics, mortality rates for asthma have been increasing steadily over the past decades. Mortality and markers of risk of death from asthma were studied among asthmatics attending a chest clinic in Copenhagen between 1974 and 1990.
Methods: The study group consisted of 1,075 asthmatics in whom the diagnosis of asthma had been verified by objective/paraclinical criteria; they were compared with a sex- and age-matched group of nonasthmatic patients. Both groups of subjects comprised 425 men (mean age, 37.3 years [SD 15.2]) and 650 women (mean age, 38.5 years [SD 16.0]), and the mean follow-up period was 8.6 years (SD 4.2) in both asthmatics and controls.
Results: Mortality from all causes was significantly increased in the asthmatic subjects (93 deaths) compared with the control group (41 deaths); relative risk [RR], 2.4; 95% confidence interval [CI], 1.6 to 3.4). The predominant cause of excess mortality was obstructive pulmonary disease, that is, status asthmaticus (14 vs 0 deaths, RR 8.2) and COPD not classified as status asthmaticus (19 vs 0 deaths, RR 8.3). Overall, 91% of the asthmatic cohort survived the mean follow-up period of almost 9 years compared with 96% of the controls. Mortality analysis employing the multiple regression model of Cox revealed that age, pack-years of smoking, eosinophilia, level of FEV1 percent predicted, and degree of reversibility in FEV1 were significant predictors of death from asthma, whereas no association was found between previous hospital admissions for asthma and subsequent death from asthma. In subjects with eosinophil (> 0.45 mia [10(9)/L]), the risk of dying from asthma was 7.4 (CI 2.8 to 19.7) greater than in those without eosinophilia. Compared with subjects with 15 to 24% reversibility in FEV1, the subjects with 25 to 49% and > 50% reversibility had a 2.7 and 7.0 higher risk of death from asthma, respectively.
Conclusion: Mortality was significantly increased in asthmatics compared with matched controls, primarily because of death from acute and chronic asthma. Furthermore, the present findings suggest that eosinophilia and pronounced increase in FEV1 after bronchodilator are strong markers of subsequent risk of death from asthma.