Data from long-term follow-up studies of patients with well-characterized asthma are limited. We studied all-cause and cause-specific mortality and risk factors in a large cohort of adults with asthma.
A total of 1,075 adult patients with asthma were recruited consecutively from an outpatient clinic from 1974 to 1990 and followed up until the end of 2011. Subjects were classified as having allergic or nonallergic asthma on the basis of a detailed history, spirometric tests, tests for IgE-mediated allergy (skin prick tests and radioallergosorbent test), and bronchial challenge tests. Information on vital status and cause of death were obtained from the Danish Death Register and the Danish National Board of Health. All-cause mortality was also studied in an age- and sex-matched group of subjects without asthma.
All-cause mortality was increased significantly among patients with asthma compared with control subjects (261 cases vs 124 control subjects; relative risk (RR), 2.1; 95% CI, 1.4-3.0; P < .001). The excess mortality was primarily due to death from obstructive lung disease (95 deaths). Subsequent death from asthma was significantly associated with age (P < .001), level of FEV1 % predicted (P < .001), bronchodilator reversibility (P < .01), peripheral eosinophil count (P < .0001), and previous acute hospital contacts for asthma (P = .002) at enrollment. No significant association was found between smoking habits or self-reported symptom severity, and subsequent death from asthma. After adjusting for age and level of FEV1 % predicted, nonallergic asthma was associated with a higher risk of death from asthma (RR, 1.9; 95% CI, 1.1-3.2; P = .001).
This 25-year prospective study of a large cohort of adults with well-characterized asthma showed an excess mortality compared with matched control subjects, to a large extent explained by death from obstructive lung disease.