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