title: Evidence of confounding by smoking of associations between radiation and lung cancer mortality among workers at the Savannah River Site.
abstract: BACKGROUND
  This study investigates confounding by cigarette smoking of associations between occupational exposure to ionizing radiation and lung cancer mortality among workers at the Savannah River Site (SRS).
  
  
  METHODS
  Thirteen thousand two hundred sixty-five white males hired at SRS between 1950 and 1986 were followed through 2002 to ascertain causes of death. Estimates of radiation doses from external sources and internal tritium uptakes were derived from dosimetry records. Logistic regression methods were used to derive discrete-time estimates of rate ratios. An indirect approach to control for unmeasured confounding by smoking was employed that involves joint modeling of lung cancer and chronic obstructive pulmonary disease (COPD) mortality.
  
  
  RESULTS
  Prior to indirect adjustment for smoking, there was minimal evidence of association between lung cancer mortality and cumulative radiation dose under a 10-year lag assumption (RR at 100 mSv = 0.90; 90% CI: 0.80-1.01). Subsequent to indirect adjustment for smoking, the association between lung cancer mortality and cumulative radiation dose under a 10-year lag was positive (RR at 100 mSv = 1.33; 90% CI: 1.01-1.77).
  
  
  CONCLUSIONS
  In this cohort, there is evidence of negative confounding of radiation dose–lung cancer mortality associations by cigarette smoking.
authors: Department of Epidemiology, School of Public Health, University of North Carolina, Chapel Hill, North Carolina 27599, USA. david.richardson@unc.edu
authors: David B
authors: DB
authors: Richardson
authors: Steve
authors: S
authors: Wing
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016001:Confidence Intervals; D015986:Confounding Factors, Epidemiologic; D019317:Evidence-Based Medicine; D006801:Humans; D016015:Logistic Models; D008175:Lung Neoplasms / Q000453:epidemiology / Q000209:etiology / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D009657:North Carolina / Q000453:epidemiology; D055848:Nuclear Power Plants / Q000706:statistics & numerical data*; D016273:Occupational Exposure / Q000009:adverse effects / Q000706:statistics & numerical data*; D011830:Radiation Effects; D011839:Radiation, Ionizing; D012306:Risk; D018570:Risk Assessment; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D014316:Tritium / Q000633:toxicity
chemical_list: D014316:Tritium