Air pollution and Venous Thromboembolism in the Malmö Diet and Cancer cohort

Background: Air pollution is a major contributor to the global burden of disease and has been linked to several diseases and conditions. The mechanisms are related to inflammation and increased coagulability, factors that play an important role in the pathogenesis of venous thromboembolism (VTE). We investigated if long-term exposure to air pollution was associated with increased VTE incidence. Methods: The study followed 29,408 participants from the Malmö Diet and Cancer (MDC) cohort. The population-based cohort recruited adults aged 44-74 from Malmö, Sweden between 1991-1996. Participants were assigned annual mean residential exposure to particulate matter <2.5μg (PM2.5) and <10μg (PM10), nitrogen oxides (NOx) and black carbon (BC) from enrollment up to 2016. Those with previous VTE events or VTE occurring close to a malignancy diagnosis were excluded from main analysis. Analyses were done using Cox proportional hazard models for air pollution in the year of VTE event (lag0) and the mean of 1-10 years before VTE event (lag1-10). VTE was defined as deep vein thrombosis (DVT) of the legs and pulmonary embolism (PE). Results: The means of annual air pollution exposure during the observation period were 15.8μg/m3 for PM10, 10.8μg/m3 for PM2.5, 27.7μg/m3 for NOx, and 0.96μg/m3 for BC. The mean follow-up period was 19.5 years, with 1418 VTE events recorded during this period. Exposure to lag1-10 PM2.5 was associated with increased risk of VTE (HR 1.17(95%CI 1.01–1.37) per 0.75μg/m3(IQR) increase in PM2.5 exposure) when adjusting for likely confounders. No association was found with lag0 air pollution exposure. Similar results were found for DVT, but no association was observed with PE. Results persisted in sensitivity analyses. Conclusion: Long-term exposure to moderate levels of ambient air pollution was associated with increased risks of VTE in the general population in Sweden. Keywords: Air pollution, venous thromboembolism, survival analysis, deep vein thromboembolism.