Interactions between cigarette smoking and ambient PM 2.5 for cardiovascular mortality

Environ Res. 2017 Apr;154:304-310. doi: 10.1016/j.envres.2017.01.024. Epub 2017 Jan 28.

Abstract

Associations between long-term exposure to ambient fine particulate matter (PM2.5) and all-cause and cardiovascular mortality are well documented however less is known regarding possible interactions with cigarette smoking. We previously reported a supra-additive synergistic relationship between PM2.5 and cigarette smoking for lung cancer mortality. Here we examine interactions for all-cause and cardiovascular mortality among 429,406 current or never smoking participants in the prospective American Cancer Society Cancer Prevention Study-II with modeled PM2.5 concentrations. Cox proportional and additive hazards models were used to estimate mortality associations and interactions on the multiplicative and additive scales. A total of 146,495 all-cause and 64,339 cardiovascular (plus diabetes) deaths were observed. The hazard ratio (HR) (95% confidence interval (CI)) for cardiovascular mortality for high vs. low PM2.5 exposure (>14.44µg/m3 vs ≤10.59µg/m3, 75th vs 25th percentile) was 1.09 (95% CI 1.05, 1.12) in never smokers. The HR for cigarette smoking was 1.89 (95% CI 1.82, 1.96) in those with low PM2.5. The HR for both high PM2.5 and cigarette smoking was 2.08 (95% CI 2.00, 2.17). A small significant excess relative risk due to interaction (0.10; 95% CI 0.02, 0.19) was observed. Quantification of the public health burden attributed to the interaction between PM2.5 and cigarette smoking indicated a total of 32 (95% CI -6, 71) additional cardiovascular deaths per 100,000 person-years due to this interaction. In conclusion, PM2.5 was associated with all-cause and cardiovascular mortality in both smokers and never smokers, with some evidence for a small additive interaction with cigarette smoking. Reductions in cigarette smoking will result in the greatest impact on reducing all-cause and cardiovascular death at the levels of PM2.5 observed in this study. However, reductions in PM2.5 will also contribute to preventing a proportion of mortality attributed to cigarette smoking.

Keywords: Additive interaction; Air pollution; Cardiovascular mortality; Cigarette smoking; Particulate matter.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Cardiovascular Diseases / epidemiology
  • Cardiovascular Diseases / etiology*
  • Cardiovascular Diseases / mortality*
  • Cohort Studies
  • Female
  • Humans
  • Male
  • Middle Aged
  • Particulate Matter / adverse effects*
  • Prospective Studies
  • Smoking / adverse effects*
  • United States / epidemiology

Substances

  • Particulate Matter

Grant support