Impact of neighborhood socioeconomic status on the association between occupational radiation exposure and circulatory disease

Abstract

Background: Exposure to ionizing radiation, even at low-to-moderate doses, increases the risk of circulatory disease (CD) incidence and mortality. The risk of CD is also influenced by an individual’s social environment, and this may modify the effect of occupational exposures like ionizing radiation. Aim: We examined the effect of neighborhood socioeconomic status (nSES) on incidence and mortality from overall CD, ischemic heart disease (IHD) and cerebrovascular disease (CeVD) in the US Radiologic Technologists Study (USRT) between 1994 and 2012. Additionally, we assessed whether nSES confounds and/or modifies the association between occupational radiation exposure and CD outcomes. Methods: Cumulative radiation dose (mGy) was estimated for each participant. We created tertiles of nSES combining six items from the 1990 Census (household income, housing value, % households with interest/income, % adults who completed high school, % adults who completed college, % of persons in managerial occupations). Using discrete time hazard models, we estimated HR and 95%CI for the association between radiation, nSES and CD outcomes. Results: Compared to residents from the top nSES tertile, technologists from low-nSES areas had an elevated risk of overall CD mortality, IHD mortality and incidence, and CeVD incidence (HRs ranging from 1.18 to 1.25, 95%CIs:1.07-1.42), but not for CeVD mortality (HR: 0.92, 95%CI: 0.75-1.15) adjusting for radiation and individual education. We found no evidence of confounding by nSES on the association between radiation and any CD outcomes. There was evidence of a multiplicative interaction between nSES tertiles and radiation exposure for all mortality outcomes (p-value for interaction: <0.001 for overall CD, 0.003 for IHD and 0.004 for CeVD), but not for incidence. Conclusion: nSES is independently associated with CD mortality and incidence in a group of US radiologic technologists occupationally exposed to radiation. Additionally, nSES modifies (but does not confound) the association between radiation and CD mortality outcomes.