Air Pollution Preconditions for Heart Attacks

A retrospective cohort study of stroke onset: Implications for characterizing short term effects from ambient air pollution (27 page pdf, Julie YM Johnson, Paul J Villeneuve, Dion Pasichnyk and Brian H Rowe, Environmental Health, Oct. 6, 2011)

Today we review an interesting look at what difference it makes when using the date that a stroke patient is taken to hospital (vs. the time of stroke onset) and using the level of local pollution at the residence(vs. ambient level for city). Conclusion is that it makes little difference in this case- but may when the patient is more mobile or when the patient is exposed to pockets of high pollution.



Key Quotes:

“the onset of stroke symptoms frequently occurred more than one full calendar day before hospital admission, and that the impact from this misclassification of the timing of stroke onset produces air pollution risk estimates that may be understated by as much as 40%”

“a study of models of traffic-related pollution estimates that included time-activity patterns suggested that the difference between the mobility-based model and residence-only models may lead to risk estimates biased toward the null”

“to examine the extent of misclassification of exposure based on data on patient residence and hospital admission time and date to increase our understanding of the possible biases in ambient air pollution risk estimates arising from the use of administrative datasets.”

“A systematic difference in ambient NO2 and PM2.5 levels could not be detected between day of stroke onset and day of presentation to hospital”

“a very high proportion of stroke patients were indoors during stroke onset…adult Canadians spend more than ¾ of their time indoors, even in summer months.. Personal exposure to NO2 and PM2.5 can be different than background exposure measurements, and in Canada the difference can be dependent on season, the use of gas heating, gas stoves, and air conditioning”

“Our data suggest that day of presentation and residential location data obtained from administrative records reasonably captures the time and location of stroke onset for most patient”

Related articles

• The Link Between Air Pollution and Asthma (everydayhealth.com)
• Exposure to Air Pollution and Heart Attacks (pollutionfree.wordpress.com)
• Attacks on federal air pollution regulations dangerous to Americans' health (eurekalert.org)
• Could Pollution Increase Lung Cancer Risk? (huffingtonpost.com)