| The type of stroke that results when a blood clot | | | | of hemorrhagic stroke, which is caused by |
| travels to the brain -- called an ischemic stroke -- | | | | bleeding in the brain, during the same "high |
| is more likely to occur on days when the air | | | | pollution" days, notes Wellenius, but found no |
| contains a larger concentration of particulate | | | | association between the two.Reducing Exposure |
| matter, according to a study published online in | | | | May Lower RiskThe air pollution in question -- |
| Stroke: Journal of the American Heart | | | | particulate matter smaller than 10 micrometers in |
| Association.Researchers at Beth Israel Deaconess | | | | diameter -- includes particles from car and truck |
| Medical Center (BIDMC) and the Harvard School | | | | exhaust, power plants and refineries. The |
| of Public Health (HSPH) examined air quality on a | | | | measurements were provided by the US |
| total of 37,000 days in nine cities. Risk of | | | | Environmental Protection Agency from nine US |
| hospitalization for ischemic stroke was 1 percent | | | | cities: Birmingham, Ala., Chicago, New Haven, |
| higher on days with relatively high levels of air | | | | Conn., Cleveland, Detroit, Minneapolis, Pittsburgh, |
| pollution, compared with low-air pollution days, | | | | Salt Lake City and Seattle.The authors analyzed |
| reports lead author Gregory Wellenius, ScD, | | | | hospital admissions among a group of Medicare |
| postdoctoral fellow in cardiology at BIDMC.Third | | | | patients with an average age of 79. Seventy-five |
| Cause of Death in US"Although these effects | | | | percent of the patients were white, and 61 |
| sound relatively small," says Wellenius, "given the | | | | percent were female. Their findings showed that |
| large number of people exposed to air pollution | | | | during the course of their study, there were |
| and the large number of people at risk for stroke | | | | 155,503 hospital admissions for ischemic |
| ... the actual number of strokes could be | | | | stroke.The final analysis demonstrated a 1.03 |
| significant."Stroke is the third leading cause of | | | | percent rise in ischemic stroke on the days with |
| death in the US, affecting more than 700,000 | | | | the highest pollution measures."We don't know |
| individuals each year.A "consistent increased risk" | | | | exactly what mechanisms are involved that |
| for cardiac health problems associated with | | | | trigger these cardiac events," says Wellenius. |
| exposure to ambient air particles was established | | | | "However, we do know that particulates in the air |
| in earlier research by Wellenius and coauthors | | | | promote inflammation, which is a significant risk |
| Murray Mittleman, MD, DrPH, of BIDMC's | | | | factor for cardiac events; that exposure to |
| Cardiovascular Epidemiology Research Unit and | | | | particulates can lead to changes in heart rate and |
| Joel Schwartz, PhD, of HSPH."Air pollution has | | | | blood pressure; and that pollution can cause |
| been shown to trigger heart attacks and to | | | | changes in coaguable states (related to blood |
| aggravate the conditions of patients with | | | | clotting abilities)."The authors say that future |
| congestive heart failure," says Mittleman, who is | | | | research will focus on finding out which pollutants |
| also an associate professor of medicine at | | | | are most toxic, as well as which patients are at |
| Harvard Medical School."These new findings, | | | | greatest risk for health problems stemming from |
| demonstrating that incidence of clot-based | | | | air pollution."Taken together with previous work, |
| strokes also increase, [are] in keeping with our | | | | these latest results support the idea that reducing |
| earlier data showing a relationship between air | | | | exposure to particulate matter may reduce the |
| pollution and heart and lung disorders," he | | | | risk of strokes and heart attacks," they conclude. |
| notes.The researchers also looked at the incidence | | | | |