New link between air pollution and stroke

Reported by Susan Aldridge, PhD, medical journalist

Hourly air pollution rates affect stroke risk, according to new research.
It is already known that daily levels of increased particulate air pollution have an adverse impact on lung and heart disease. Now researchers in Japan reveal that hourly changes in air pollution levels could be significant in the case of intracerebral hemorrhage, the type of stroke caused by a burst blood vessel in the brain.

They looked at data on stroke deaths for people aged 65 or more in Japan between 1990 and 1994 in 13 major urban areas. Levels of air pollution - nitrogen dioxide, particles and photochemical oxidants - were measured hourly during this time. Stroke caused by intracerebral hemorrhage proved more likely in the warmer months between April and September. What is more, high hourly rates of particulate air pollution two hours before death were linked to a more than doubling of the risk of death from this kind of stroke.

No such link was found for ischemic stroke, where the arteries in the brain are blocked by a clot. This is the more common cause of stroke. The researchers think the tight time link seen between particulate air pollution and intracerebral hemorrhage stroke might be that this kind of stroke causes death more rapidly. The findings suggest that maybe air pollution monitoring should be looked at on an hourly, rather than daily, level.

Source
Occupational and Environmental Medicine online 20th September 2006

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