Effects of Air Pollutants on Acute Stroke Mortality. (Articles)
Hong, Yun-Chul, Lee, Jong-Tae, Kim, Ho, Ha, Eun-Hee, Schwartz, Joel, Christiani, David C., Environmental Health Perspectives
The relationship between stroke and air pollution has not been adequately studied. We conducted a time-series study to examine the evidence of an association between air pollutants and stroke over 4 years (January 1995-December 1998) in Seoul, Korea. We used a generalized additive model to regress daily stroke death counts for each pollutant, controlling for seasonal and long-term trends and meteorologic influences, such as temperature, relative humidity, and barometric pressure. We observed an estimated increase of 1.5% [95% confidence interval (CI), 1.3-1.8%] and 2.9% (95% CI, 0.3-5.5%) in stroke mortality for each interquartile range increase in particulate matter < 10 [micro]m aerodynamic diameter (P[M.sub.10]) and ozone concentrations in the same day. Stroke mortality also increased 3.1% (95% CI, 1.1-5.1%) for nitrogen dioxide, 2.9% (95% CI, 0.8-5.0%) for sulfur dioxide, and 4.1% (95% CI, 1.1-7.2%) for carbon monoxide in a 2-day lag for each interquartile range increase in single-pollutant models. When we examined the associations among P[M.sub.10] levels stratified by the level of gaseous pollutants and vice versa, we found that these pollutants are interactive with respect to their effects on the risk of stroke mortality. We also observed that the effects of P[M.sub.10] on stroke mortality differ significantly in subgroups by age and sex. We conclude that P[M.sub.10] and gaseous pollutants are significant risk factors for acute stroke death and that the elderly and women are more susceptible to the effect of particulate pollutants. Key words: air pollution, mortality, stroke. Environ Health Perspect 110:187-191 (2002).
[Online 17 January 2002]
Stroke is a common cause of death and a leading cause of long-term severe disability. Despite widespread concern and the great health burden imposed on the middle-aged and elderly, the relationship between stroke and environmental risk factors such as air pollution has not been studied adequately. Recent reviews on the effect of particulate matter of aerodynamic diameter < 10 [micro]m (P[M.sub.10]) on mortality suggest that a rise of 10 [micro]g/[m.sup.3] in P[M.sub.10] is associated with an increase in the daily total mortality of 1% (1,2). Some epidemiologic studies have also reported associations between gaseous pollutants, such as S[O.sub.2], N[O.sub.2], and CO, and mortality (3-5). However, relatively few studies have attempted to quantify the specific effects of air pollution on stroke mortality, although a number of studies have demonstrated an increased risk of cardiovascular mortality associated with air pollution (6-8). Because air pollution is a potentially modifiable risk factor that does not rely on behavioral change, we thought it worthwhile to explore the relationship between air pollution and stroke. By focusing on the preventive aspects of stroke, we can reduce stroke-related health problems more significantly than by the acute management of stroke patients after stroke occurs (9).
Pollution is composed of various mixtures from diverse emitting sources. Because it is very difficult to separate one pollutant effect from another and because the effect of one pollutant may be influenced by those of others, interactions among pollutants should be considered rather than the effects of just single pollutant.
Seoul, Korea, presents a useful model for studying effects of air pollutants on stroke because of the high concentrations of particulate pollutants and the high stroke mortality (72.9 per 100,000 population annually). It is the biggest Korean metropolitan area and is located centrally on the Korean peninsula. Mean population size during this study period (1995-1998) was 10.6 million and the major air pollution source was automobile exhaust emissions. Korea has a four-season climate and an annual temperature range of--11. …