Long-term exposure to air pollution is associated with the risk of venous thromboembolism

A large study found that greater exposure to long-term air pollution was linked to increased risks for blood clots that can form in the deep veins, which, if left untreated, can block blood flow and cause serious complications, even and death.

These findings emerged from a longitudinal study funded by the National Institutes of Health (NIH) that included 6,651 US adults who were followed for an average of 17 years between 2000 and 2018. Participants lived in or near one of six major metropolitan areas. regions: New York, Baltimore, Chicago, Los Angeles, Minneapolis and Winston-Salem, North Carolina.

Throughout the study, 248 adults, 3.7% of the study sample, developed deep vein blood clots that required hospital care. The likelihood of this outcome was associated with anywhere from a 39% to more than twofold increased risk based on long-term exposure to three different types of air pollutants.

Blood clots in the deep veins, known collectively as venous thromboembolism (VTE), include deep vein thrombosis, which occurs when a blood clot forms in a deep vein of the legs, arms, or an internal organ, and pulmonary embolism, which occurs when a blood clot breaks off from a deep vein and travels to the lungs.

Exposure to air pollution, which can create inflammation and contribute to blood clotting, has long been linked to cardiovascular and respiratory disease. While previous research has also suggested a link to VTE, this is the largest, most comprehensive US study reporting this association with three different types of air pollutants.

This included exposure to tiny air pollution particles 2.5 micrometers or smaller, which can be inhaled from a variety of sources, including smoke from coal-fired power plants, forest fires and vehicle exhaust. Participants with higher overall exposure to this type of air pollution had a 39% increased risk of VTE compared to people exposed to lower levels. People with increased exposure to nitrogen oxides and nitrogen dioxide, pollutants most commonly found in vehicle exhaust, had a 121% to 174% increased risk, respectively.

To reach these findings, the researchers analyzed the relationship between patients hospitalized for VTE and air pollution levels collected through extensive two-week community-wide monitoring. including samples taken from participants’ homes. They then compared those with the highest levels of exposure -? the top 75% -? to those with the lowest exposure -; the bottom 25%. They also conducted multiple analyzes to control for variables associated with VTE, such as age, smoke exposure, and underlying respiratory and other health conditions.

VTE affects up to 900,000 Americans each year. Many cases occur after surgery, but other factors, such as age, long periods of inactivity, heart disease, pregnancy, and genetics, can increase the risks.

The research, part of the Multinational Study of Atherosclerosis (MESA), was funded by contracts and grants from the NIH’s National Heart, Lung, and Blood Institute and the National Center for Advancing Translational Sciences and the Environmental Protection Agency.