Increased rates of asthma among World Trade Center disaster responders

Background: Studies have documented high rates of asthma symptoms among responders to the World Trade Center (WTC) disaster. However, whether there are increased rates of asthma among responders compared to the general population is unknown. Methods: The study population consisted of a prospective cohort of 20,834 responders participating in the WTC Medical Monitoring and Treatment Program between July 2002 and December 2007. We calculated prevalence and standardized morbidity ratios (SMRs) of lifetime asthma and 12-month asthma (defined as ≥1 attacks in the prior 12 months) among WTC responders. The comparison population consisted of >200,000 adults who completed the National Health Interview Survey in 2000 (for pre-9/11 comparisons) and between 2002 and 2007 (for post-9/11 comparisons). Results: WTC responders were on average 43±9 years old, 86% male, 59% white, and 42% had an occupation in protective services. The lifetime prevalence of asthma in the general population was relatively constant at about 10% from 2000 to 2007. However, among WTC responders, lifetime prevalence increased from 3% in 2000, to 13% in 2002, and 19% in 2007. The age-adjusted overall SMR for lifetime asthma among WTC responders was 1.8 (95% CI: 1.8-1.9) for men and 2.0 (95% CI: 1.9-2.1) for women. Twelve-month asthma was also more frequent among WTC responders compared to the general population (SMR 2.4, 95% CI: 2.2-2.5) for men and 2.2 (95% CI: 2.0-2.5) for women. Conclusions: WTC responders are at an increased risk of asthma as measured by lifetime prevalence or active disease.