A large study found that greater exposure to long-term air pollution was linked with increased risks for blood clots that can occur in deep veins, which, if untreated, can block blood flow and cause serious complications, even death.
These findings came from a longitudinal study funded by the National Institutes of Health (NIH) that included 6,651 U.S. 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: New York, Baltimore, Chicago, Los Angeles, Minneapolis, and Winston-Salem, North Carolina.
Air pollution linked to increased risks for venous thromboembolism
Throughout the study, 248 adults, 3.7% of the study sample, developed blood clots in deep veins that required hospital care. The likelihood of this outcome was linked to anywhere from a 39% to a more than two-fold increased risk based on long-term exposure to three different types of air pollutants.
Blood clots in deep veins, collectively known 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 set the stage for inflammation and contribute to blood clotting, has long been associated with cardiovascular and respiratory diseases. While previous research has also suggested a link to VTE, this is the largest, most comprehensive U.S. study to report that association with three different types of air pollutants.
- Up to 900,000 people in the United States are affected by venous thromboembolism (VTE, a blood clot), each year
- People are at particularly high risk for VTE during or just after a hospitalization (with or without surgery), during cancer treatment, and during or just after pregnancy
- An estimated 60,000-100,000 Americans die of VTE each year and many others have long-term complications from a VTE
This included exposure to tiny air pollution particles equal to or less than 2.5 micrometers(link is external), which can be inhaled from a variety of sources, including smoke from coal-burning power plants, forest fires, and motor vehicle exhaust. Participants with greater overall exposure to this type of air pollution had a 39% increased associated risk for VTE compared to people exposed to lower levels. People with increased exposure to oxides of nitrogen(link is external) and nitrogen dioxide(link is external), pollutants most often found from vehicle exhaust, had a respective 121% to 174% increased risk.
To reach these findings, the researchers analyzed the relationship between patients hospitalized for VTE and levels of air pollution collected through extensive biweekly community-level monitoring — including samples taken from the homes of participants. They then compared those with the highest exposure levels — the top 75% — to those with the lowest exposure — the bottom 25%. They also conducted multiple analyses to control for variables associated with VTE, such as age, exposure to tobacco, and underlying respiratory and other health conditions.
VTE affects up to 900,000 Americans(link is external) each year. Many cases occur after surgery, but other factors, including age, long periods of inactivity, heart disease, pregnancy, and genetics, can increase risks.
Healthcare-associated VTE
More than a third of VTE cases diagnosed each year are related to a recent hospitalization and most of these do not occur until after discharge.
VTE is a leading cause of preventable hospital death in the United States.
VTE is the fifth most frequent reason for unplanned hospital readmissions after surgery, overall, and the third most frequent among patients undergoing total hip or knee joint replacement.
As many as 70% of cases of healthcare-associated VTE are preventable through measures such as use of anticoagulant medications or compression stockings. Yet fewer than half of hospital patients receive these measures.
Cancer and VTE
An estimated one in five cases of VTE are related to cancer and its treatment.
The risk is greatest in the first few months after a cancer diagnosis, the time when treatment generally occurs.
Among people with cancer, survival rates are lower for people who also have a VTE.
Pregnancy and VTE
Women are five times more likely to experience a VTE during pregnancy, childbirth, or the 3-month period after delivery.
PE is one of the most common causes of pregnancy-related death in the United States.
Complications
One-third (about 33%) of people with a VTE will have a recurrence within 10 years.
Among people who have had a DVT, one third to one half will have long-term complications (post-thrombotic syndrome) such as swelling, pain, discoloration, and scaling in the affected limb.
Chronic thromboembolic pulmonary hypertension is a complication that can happen after a PE with a large clot. It can stop blood from reaching the lungs and can be fatal.
Discussion about this post