Standardized morbidity ratios of four chronic health conditions among World Trade Center responders: Comparison to the National Health Interview Survey

Purpose: We conducted external comparisons for the prevalence of asthma, hypertension, diabetes, and cancer among World Trade Center (WTC) general responders using the National Health Interview Survey (NHIS) as the reference, along with internal comparisons for the incidence of asthma. Methods: Standardized Morbidity Ratios (SMRs) were calculated for the prevalence of the health conditions, and risk ratios (RRs) for asthma incidence. Results: Relative to the NHIS, asthma prevalence was in excess in responders over the study years (age-adjusted SMRs = 1.3-2.8). Hypertension prevalence began to exceed expected from 2006 while diabetes was lower than expected. An upward trend towards excess cancer prevalence was observed. Internal comparisons showed elevated asthma incidence among protective service and utility workers compared to construction workers; while those who arrived at the WTC site in the morning of 9/11 had a lower asthma risk than those who arrived in the afternoon. Conclusions: The use of NHIS data as a reference population demonstrates and reconfirms several important patterns of excess risk in WTC responders. External comparisons are an alternative for disaster cohorts without an established comparison group.