Ethnic differences in ambient air pollution and risk of acute ischemic stroke

Abstract

Objectives: To investigate the association between short-term changes in ambient pollution (particulate matter <2.5 μm in aerodynamic diameter (PM2.5) and ozone (O3)) and the risk of ischemic stroke among individuals living in a bi-ethnic community and whether this association is modified by ethnicity.

Methods: We identified incident ischemic stroke cases from the population-based Brain Attack Surveillance in Corpus Christi (BASIC) project between 2000 and 2012. Associations between PM2.5 (mean 24-h) and O3 (maximal 8-h) levels, measured on the same-day and lags of 1-3 days, and odds of ischemic stroke were assessed using a time-stratified case-crossover design and modeled using conditional logistic regression. We explored race/ethnicity (Mexican American versus non-Hispanic white) as a modifier by including interaction terms in the models.

Results: There were 2948 ischemic strokes with median age 71 years (IQR: 59-80). We observed no overall associations between the air pollutants and odds of ischemic stroke at any lag. When stratified by ethnicity, higher O3 was consistently associated with greater odds of ischemic stroke for non-Hispanic whites, but not for Mexican Americans. Higher PM2.5 was generally associated with lower odds of ischemic stroke for non-Hispanic whites but modestly greater odds for Mexican Americans.

Conclusion: Ethnic differences in the associations between ischemic stroke and short-term exposures to O3 and PM2.5 were suggested indicating that further study in diverse populations may be warranted.

Keywords: Air pollution; Ethnicity; Ischemic stroke; Ozone; PM(2.5).

Figure 1

Odds ratios associated with a 10 μg/m³ increase in 24-hour PM_2.5 overall and stratified by ethnicity for 2000-2012 incident ischemic stroke cases in Nueces County, Texas. NHW corresponds to non-Hispanic White ethnicity and MA corresponds to Mexican American ethnicity.

Figure 2

Odds ratios associated with a 10 ppb increase in maximal 8-hour O₃ overall and stratified by ethnicity for 2000-2012 incident ischemic stroke cases in Nueces County, Texas. NHW corresponds to non-Hispanic White ethnicity and MA corresponds to Mexican American ethnicity.