A cohort study evaluating the risk of stroke associated with long-term exposure to ambient fine particulate matter in Taiwan

Abstract

Background Evidences have shown that the stroke risk associated with long-term exposure to particulate matter with an aerodynamic diameter of ≤2.5 μm (PM2.5) varies among people in North America, Europe and Asia, but studies in Asia rarely evaluated the association by stroke type. We examined whether long-term exposure to PM2.5 is associated with developing all strokes, ischemic stroke and hemorrhagic stroke. Methods The retrospective cohort study consisted of 1,362,284 adults identified from beneficiaries of a universal health insurance program in 2011. We obtained data on air pollutants and meteorological measurements from air quality monitoring stations across Taiwan in 2010–2015. Annual mean levels of all environmental measurements in residing areas were calculated and assigned to cohort members. We used Cox proportional hazards models to estimate hazard ratio (HR) and 95% confidence interval (CI) of developing stroke associated with 1-year mean levels of PM2.5 at baseline in 2010, and yearly mean levels from 2010 to 2015 as the time-varying exposure, adjusting for age, sex, income and urbanization level. Results During a median follow-up time of 6.0 years, 12,942 persons developed strokes, 9919 (76.6%) were ischemic. The adjusted HRs (95% CIs) per interquartile range increase in baseline 1-year mean PM2.5 were 1.03 (1.00–1.06) for all stroke, 1.06 (1.02–1.09) for ischemic stroke, and 0.95 (0.89–1.10) for hemorrhagic stroke. The concentration-response curves estimated in the models with and without additional adjustments for other environmental measurements showed a positively linear association between baseline 1-year mean PM2.5 and ischemic stroke at concentrations greater than 30 μg/m3, under which no evidence of association was observed. There was an indication of an inverse association between PM2.5 and hemorrhagic stroke, but the association no longer existed after controlling for nitrogen dioxide or ozone. We found similar shape of the concentration-response association in the Cox regression models with time-varying PM2.5 exposures. Conclusion Long-term exposure to PM2.5 might be associated with increased risk of developing ischemic stroke. The association with high PM2.5 concentrations remained significant after adjustment for other environmental factors.

Joint Exposure to Ambient Air Pollutants, Genetic Risk, and Ischemic Stroke: A Prospective Analysis in UK Biobank

“…33 Similarly, positive association between IS and measures of PM 2.5 and NO 2 by 2 cohort studies. 34,35 However, a cohort from the southeastern United States did not observe any association between PM 2.5 and IS. 36 In addition, a recent cohort study from the public health care system in Catalonia and Spain discovered that exposure to NO 2 but not PM 2.5 was associated with an increased risk of IS.…”

Fine Particulate Matter Exposure, Genetic Susceptibility, and the Risk of Incident Stroke: A Prospective Cohort Study

“…For example, both the Danish Nurses cohort study and the Taiwan Chinese cohort study reported that chronic PM 2.5 exposure was related to an increased risk of ischemic stroke but not hemorrhagic stroke. 6,23 On the contrary, the Ontario Population Health and Environment Cohort from Canada demonstrated an increased risk of both stroke subtypes with higher PM 2.5 exposures. 24 The inconclusive findings may result from the misclassification of stroke subtypes, narrow range of PM 2.5 exposure levels, and relatively short follow-up durations.…”

“…However, existing evidence on the association of PM 2.5 with stroke subtypes is still insufficient and inconclusive. [4][5][6] Most of the studies supported a significant association between PM 2.5 and ischemic stroke, while the results for hemorrhagic stroke remain controversial. 4 Furthermore, compared with Western countries, Asian populations, including Chinese and Japanese, have a higher incidence of overall stroke and proportion of hemorrhagic stroke.…”

Long-term ambient hydrocarbon exposure and incidence of urinary bladder cancer

“…Seven clusters of urbanization stratification were grouped into four levels: high, medium–high, medium, and low urbanization, according to the previously published consensus methodology 45 . Clusters of high bladder cancer incidence rate in the black-foot disease endemic regions included six southwestern coastal townships where people unknowingly drank arsenic-contaminated well water before tap water installation in 1979–2003 46 – 48 .…”