Short-term increases in traffic-related nitrogen oxides are associated with acute venous thromboembolism admissions: An 18-year data linkage study in Scotland

Introduction Chronic exposure to air pollution is strongly associated with subsequent development of cardiovascular conditions, including the development of Venous thromboembolism (VTE), however short-term effects have been less well explored. Aim To determine whether short-term variations in air quality are associated with hospital admissions for venous thromboembolism (VTE). Methods We conducted a time-series analysis using routinely collected hospital admission data from Ninewells Hospital, Dundee, Scotland (2000–2017). Outcomes included hospital admissions for deep vein thrombosis only (DVT), pulmonary embolism only (PE) or DVT & PE. Air pollution types included were: Nitrogen oxides (NOx), Nitrogen dioxide (NO2), Nitric oxide (NO) and Particulate matter smaller than 10 micrometers (PM10). Associations were estimated using quasi-Poisson regression with distributed lag models, adjusting for temperature, humidity, day of week, month, year and public holiday. Risk ratios (RR) and 95% confidence intervals (CI) were calculated for a 10μg/m3 increase in air pollutant concentrations, reported for day 0 (day of exposure), and cumulative exposure over days 0-9. Outcomes/results Cumulative exposure to NO was associated with increased risk of DVT & PE admission (RR 1.03; 95% CI 1.00-1.07). PE admissions were significantly associated with cumulative NOx (RR 1.02; 95% CI 1.00-1.05) and NO exposure (RR 1.05; 95% CI 1.01-1.09). Conclusions This study provides novel evidence that short-term exposure to nitrogen oxides may increase the risk of VTE hospital admission. While arterial events such as myocardial infarction and stroke are known to cluster around high air pollution episodes, our findings suggest that venous disease may also be affected. Further research is needed to confirm these associations and clarify underlying mechanisms.