Long-term ambient air pollution and venous thromboembolism in a population-based Swedish cohort

Abstract

Air pollution is a major contributor to the global burden of disease and has been linked to several diseases and conditions, including cardiovascular disease. The biological mechanisms are related to inflammation and increased coagulability, factors that play an important role in the pathogenesis of venous thromboembolism (VTE, i.e., deep vein thrombosis or pulmonary embolism). This study investigates if long-term exposure to air pollution is associated with increased VTE incidence. The study followed 29 408 participants from the Malmö Diet and Cancer (MDC) cohort, which consists of adults aged 44–74 recruited in Malmö, Sweden between 1991 and 1996. For each participant, annual mean residential exposures to particulate matter <2.5 μg (PM2.5) and <10 μg (PM10), nitrogen oxides (NOx) and black carbon (BC) from 1990 up to 2016 were calculated. Associations with VTE were analysed using Cox proportional hazard models for air pollution in the year of the VTE event (lag0) and the mean of the prior 1–10 years (lag1-10). Annual air pollution exposures for the full follow-up period had the following means: 10.8 μg/m3 for PM2.5, 15.8 μg/m3 for PM10, 27.7 μg/m3 for NOx, and 0.96 μg/m3 for BC. The mean follow-up period was 19.5 years, with 1418 incident VTE events recorded during this period. Exposure to lag1-10 PM2.5 was associated with an increased risk of VTE (HR 1.17 (95%CI 1.01–1.37)) per interquartile range (IQR) of 1.2 μg/m3 increase in PM2.5 exposure. No significant associations were found between other pollutants or lag0 PM2.5 and incident VTE. When VTE was divided into specific diagnoses, associations with lag1-10 PM2.5 exposure were similarly positive for deep vein thrombosis but not for pulmonary embolism. Results persisted in sensitivity analyses and in multi-pollutant models. Long-term exposure to moderate concentrations of ambient PM2.5 was associated with increased risks of VTE in the general population in Sweden.