We collected 17,447 questionnaires from 10,378 WTC-exposed firefighters over the 4-year period from 2 October 2001 to 11 September 2005. During the study, firefighter compliance with scheduled periodic evaluations every 18 months, including questionnaire completion, was 85%. Most participants were male (99.8%), were white (93.6%), and never smoked (73.1%). The number of participants in each year of the serial cross-sectional analyses was 8,920 in year 1; 1,197 in year 2; 2,889 in year 3; and 4,441 in year 4. By arrival group, 16.2% (1,683) arrived during the morning on 9/11, 63.7% (6,611) during the afternoon of 9/11, 11.7% (1,215) on day 2, and 8.4% (869) on days 3–14. The overall mean (± SD) duration of work at the WTC site was 4.4 ± 2.8 months, which differed significantly by arrival group: 4.7 ± 3.0, 4.4 ± 2.8, 3.9 ± 2.5, and 3.3 ± 2.3 months for arrival groups 1–4, respectively (p < 0.0001). Comparing the group of 10,378 with the cohort of 3,722, we found small statistically significant differences in mean age (39.2 years vs. 37.3 years; p < 0.01) and percent Caucasian (93.6% vs. 94.7%; p < 0.01), whereas percent male (99.8%) and percent arrival group 1 (16.2%) were the same.
Prevalence of symptoms in cross-sectional analyses
Before 9/11, participants had rarely reported LRS: frequent cough was reported by 4.1%, dyspnea by 2.5%, and wheeze by 1.2%. In the first year (2 October 2001 to 11 September 2002), the most common LRS was frequent cough, reported by 54.2%. By year 2, the rate of frequent cough declined to 16.9%, remaining close to that level to affect 15.7% during year 4. In contrast, dyspnea and wheeze showed little change: dyspnea was reported by 40% during year 1 and 38.8% during year 4, and wheeze was reported by 34% throughout all 4post-9/11 years.
Before 9/11, reports of URS were also rare, with frequent sore throat reported by 3.2% and frequent rhinosinusitis by 4.4%. During year 1, the most common respiratory symptom was sore throat, reported by 62.4%. By year 2, the rate of sore throat declined to 36.0%, plateauing to affect 37.0% in year 4. In contrast, rhinosinusitis showed little change, varying from 45.1% to 47.8% during years 1 and 4, respectively. Before 9/11, symptoms consistent with GERD were reported by 5.2%. GERD symptoms were reported by 41.8% during year 1 and remained between 40% and 45% during all 4post-9/11 years ().
Trends in the prevalence of symptoms in 10,378 firefighters from 2001 through 2005.
Prevalence by arrival group in cross-sectional analyses
For all symptoms, earlier arrival was associated with higher prevalence in all years (all p < 0.01). For cough, dyspnea, wheeze, sore throat, and rhinosinusitis, those in arrival groups 3 and 4 experienced a greater proportion of decline over time compared with changes in earlier arrival groups (, ).
Annual prevalence of symptoms in 10,378 firefighters by arrival group (%)a
Trends in the prevalence of symptoms in 10,378 firefighters during year 1 (2001–2002) and year 4 (2004–2005) by arrival group.
Symptom progression in the cohort
A total of 3,722 firefighters completed both year 1 and year 4 questionnaires. In year 1, the mean (± SD) number of reported symptoms per person was 2.6 ± 2.0, which significantly declined to 2.2 ± 2.0 (p < 0.0001) in year 4.
On the initial questionnaire, 64.1% reported one or more LRS, 69.7% one or two URS, and 38.4% GERD. At year 4, the prevalence of any LRS declined significantly to 49.5%, largely attributable to the 69.0% decline in cough, because both dyspnea and wheeze significantly increased from 35.2% to 39.4% and from 28.9% to 34.6%, respectively (p < 0.001 for both). Similarly, we found a significant decline (p < 0.001) in any URS to 57.3%, primarily attributable to a 37.4% decline in sore throat, because rhinosinusitis significantly increased from 44.1% to 48.7% (p < 0.001). The prevalence of GERD also increased from 38.4% to 43.8% (p< 0.001).
Factors associated with symptom patterns in the cohort
We explored the relationship between arrival group and symptom patterns in the cohort with year 1 and year 4 questionnaires (n = 3,722). Earlier arrival group was consistently related to symptom persistence for LRS, URS, and GERD. Comparing earliest arriving participants (arrival group 1) with all others, arrival group 1 members were more likely to have LRS (OR = 1.8; 95% CI, 1.5–2.2), URS (OR = 1.5; 95% CI, 1.3–1.8), and/or GERD (OR = 1.9; 95% CI, 1.5–2.2) at year 4. This held true for each individual symptom as well. For LRS, persistent cough (OR = 1.7; 95% CI, 1.3–2.1), persistent dyspnea (OR = 2.0; 95% CI, 1.7–2.4), and persistent wheezing (OR = 1.8; 95% CI, 1.5–2.3) were all more likely among arrival group 1 members. A similar pattern was apparent for those with persistent URS: persistent rhinosinusitis (OR = 1.3; 95% CI, 1.1–1.6) and persistent sore throat (OR = 1.6; 95% CI, 1.3–1.9). In contrast, asymptomatic status was consistently related to later arrival status (p< 0.0001; ).
Symptom progression [no. (%)] by arrival group in the cohort (n = 3,722) at year 4.
The prevalence of smoking in the cohort was 13.5%, 11.1%, and 75.4% for current, former, and never smokers, respectively. Current and former smokers were generally overrepresented among those with persistent symptoms. We also carried out analyses comparing persons with persistent symptoms with those who recovered. We found that current smoking compared with never smoking was associated with persistent wheeze (OR = 1.5; 95 CI, 1.1–2.1), cough (OR = 1.5; 95% CI, 1.1–2.0), and GERD (OR = 1.6; 95% CI, 1.2–2.3). Former smoking compared with never smoking was not significantly associated with individual symptoms but was associated with persistent LRS (OR = 1.3; 95% CI, 1.0–1.8) and URS (OR = 1.3; 95% CI, 1.0–1.7).
Multivariate logistic regression models in the cohort predicting symptoms at year 4, either persistent or delayed onset were carried out separately for LRS, URS, and GERD outcomes. Arrival group, initial symptoms, age on 9/11, and months of work (either modified by mask/respirator use or unmodified) were independently associated with symptoms at follow-up in all models. We used the unmodified duration variable because results did not differ from those using the modified variable. Elapsed time between year 1 and year 4 questionnaires remained significant only in the LRS model. Three interaction terms—months of work and arrival group, smoking and arrival group, and months of work and mask/respirator use—were not statistically significant (all p > 0.05). The overlap between LRS, URS, and GERD was apparent, especially in the model predicting GERD, where the addition of terms for initial LRS and rhinosinusitis symptoms greatly improved the model fit. All models satisfied Hosmer-Lemeshow goodness of fit tests (–).
Multiple logistic regression models in the cohort of 3,722 firefighters [OR (95% CI)] for LRS at year 4.
Multiple logistic regression models in the cohort of 3,722 firefighters [OR (95% CI)] for GERD at year 4.