Abstract:
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Adverse upper respiratory effects of exposure to the World Trade Center (WTC) disaster site have been previously reported. We model how the effect of WTC exposure on physician-diagnosed chronic rhinosinusitis in firefighters changed over 13 years (9/11/2001-9/10/2014) using incidence models with change points. Exposure was grouped by time of arrival at the WTC site as follows: (high) morning 9/11/2001 (n=1,631); (moderate) afternoon 9/11/2001 or 9/12/2001 (n=7,082); or (low) 9/13-24/2001 (n=1,209). Piecewise exponential survival models were used to estimate incidences by exposure group, with change points in the relative incidences estimated by maximum likelihood. Due to a programmatic change, incidences dramatically increased in all exposure groups starting in 2007. We observed only one change point during the study period, 3/2012, with relative incidence (high vs. low exposure) of 1.99 (95% CI 1.65-2.39) prior to 3/2012 and no significant difference in relative incidences after 3/2012. These results show that change point models are a practical method for evaluating change(s) in exposure/response relationships over time.
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