Particulate matter in air is in some ways linked to a tendency develop blood clots in the brain that precipitate strokes, suggests a new study. While previously air pollution was found to be linked to raised risks of cardiovascular ailments, such as heart attacks, its association with stroke risks is a new development.
The study appearing in the Journal of the American Heart Association examined the relationship between everyday air pollution and Medicare insured hospital admissions for strokes in nine US cities.
Lead author of the study, Dr. Gregory A Wellenius of Boston's Beth Israel Deaconess Medical Centre said, “Our study is the first large study in the US to address this topic". The study focusing on admissions between 1986 and 1999, pertaining to ischemic (155,503 cases) and hemorrhagic strokes (19,314 cases) found that a 1.03 per cent increase of the former was directly correlated to an increase in particulate air pollution on that day. They also found a similar increase with increased air levels of carbon monoxide, nitrogen dioxide and sulfur dioxide respectively.
In contrast, the researchers found little correlation between air pollution and admissions for hemorrhagic stroke. Dr. Wellenius tried to explain the correlations with three possible mechanisms (a combination of which or individually) caused air pollution to promote strokes. He said, "One possibility is through inflammatory effects.
The other is through pulmonary reflexes that trigger changes in blood pressure or heart rate (and) a third possibility is changes in clotting factors that tend to promote more blood clots”. He said that though the increase in risk was statistically small, it could result in a large “number of excess strokes” as pollution affects large populations.
Clearly his study proved the longstanding view that a pollution free environment contributes to better health through reduced “risks of a number of health problems” inclusive of heart disease and stroke. The study went into the finer details of the routinely published air quality data for nine cities over the 37,000-day period, weighing out the propensities of various particulate components in influencing stroke risks.
The very fact that ischemic strokes are more common than hemorrhagic strokes may also be related to increased environmental pollution, but only further studies can provide pointers as to how man's environment influences his health in different ways. Survival may have improved, but overall human health appears to be deteriorating in more ways than one.
