title: The Duration of an Exposure Response Gradient between Incident Obstructive Airways Disease and Work at the World Trade Center Site: 2001-2011.
abstract: BACKGROUND
  Adverse respiratory effects of World Trade Center (WTC) exposure have been widely documented, but the length of time that exposure remains associated with disease is uncertain. We estimate the incidence of new cases of physician-diagnosed obstructive airway disease (OAD) as a function of time since 9/11/2001 in WTC-exposed firefighters.
  
  
  METHODS
  Exposure was categorized by first WTC arrival time: high (9/11/2001 AM); moderate (9/11/2001 PM or 9/12/2001); or low (9/13-24/2001). We modeled relative rates (RR) and 95% confidence intervals (CI) of OAD incidence by exposure over the first 10 years post-9/11/2001, estimating the time(s) of change in the RR with change point models. We further examined the relationship between self-reported lower respiratory symptoms and physician diagnoses.
  
  
  RESULTS
  Change points were observed at 15 and 84 months post-9/11/2001, with relative incidence rates for the high versus low exposure group of 4.02 (95% CI 2.62-6.16) prior to 15 months, 1.90 (95% CI 1.49-2.44) from months 16 to 84, and 1.20 (95% CI 0.92-1.56) thereafter. Incidence in all exposure groups increased after the WTC health program began to offer free coverage of OAD medications in month 63. Self-reported lower respiratory symptoms in the first 15 months had 80.6% sensitivity, but only 35.9% specificity, for eventual OAD diagnoses.
  
  
  CONCLUSIONS
  New OAD diagnoses are associated with WTC exposure for at least seven years. Some portion of the extended duration of that association may be due to delayed diagnoses. Nevertheless, our results support recognizing OAD among rescue workers as WTC-related even when diagnosed years after exposure.
authors.affiliation: Department of Epidemiology and Population Health and Saul B. Korey Department of Neurology, Albert Einstein College of Medicine, Bronx, New York, USA.
authors.forename: Charles B
authors.initials: CB
authors.lastname: Hall
authors.affiliation: Montefiore Medical Center, Bronx, New York, USA; Fire Department of the City of New York, Brooklyn, New York, USA.
authors.forename: Xiaoxue
authors.initials: X
authors.lastname: Liu
authors.affiliation: Montefiore Medical Center, Bronx, New York, USA; Fire Department of the City of New York, Brooklyn, New York, USA.
authors.forename: Rachel
authors.initials: R
authors.lastname: Zeig-Owens
authors.affiliation: Department of Epidemiology and Population Health, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, New York, USA; Fire Department of the City of New York, Brooklyn, New York, USA.
authors.forename: Mayris P
authors.initials: MP
authors.lastname: Webber
authors.affiliation: Division of Pulmonary Medicine, Department of Medicine, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, New York, USA.
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Aldrich
authors.affiliation: Montefiore Medical Center, Bronx, New York, USA; Fire Department of the City of New York, Brooklyn, New York, USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: Weakley
authors.affiliation: Montefiore Medical Center, Bronx, New York, USA; Fire Department of the City of New York, Brooklyn, New York, USA.
authors.forename: Theresa
authors.initials: T
authors.lastname: Schwartz
authors.affiliation: Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, New York, USA.
authors.forename: Hillel W
authors.initials: HW
authors.lastname: Cohen
authors.affiliation: Montefiore Medical Center, Bronx, New York, USA; Fire Department of the City of New York, Brooklyn, New York, USA.
authors.forename: Michelle S
authors.initials: MS
authors.lastname: Glaser
authors.affiliation: Montefiore Medical Center, Bronx, New York, USA; The Fire Department of the City of New York, Brooklyn, New York, USA.
authors.forename: Brianne L
authors.initials: BL
authors.lastname: Olivieri
authors.affiliation: Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, New York University School of Medicine, New York, New York, USA; The Fire Department of the City of New York, Brooklyn, New York, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Weiden
authors.affiliation: Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, New York University School of Medicine, New York, New York, USA; The Fire Department of the City of New York, Brooklyn, New York, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Nolan
authors.affiliation: The Fire Department of the City of New York, Brooklyn, New York, USA.
authors.forename: Kerry J
authors.initials: KJ
authors.lastname: Kelly
authors.affiliation: The Fire Department of the City of New York, Brooklyn, New York, USA; Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, New York, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Prezant