Differential effects of air pollution on ischemic stroke and ischemic heart disease by ethnicity in a nationwide cohort in the Netherlands

Abstract

BACKGROUND: Air pollution is a major risk factor for cardiovascular diseases and contributes to health disparities, particularly among minority ethnic groups, who often face higher exposure levels. Knowledge on whether the effect of air pollution on cardiovascular diseases differs between ethnic groups is crucial for identifying mechanisms underlying health disparities, ultimately informing targeted public health strategies and interventions. We explored differences in associations between air pollution and ischemic stroke and ischemic heart disease (IHD) for the six largest ethnic groups in the Netherlands. METHODS: This nationwide analysis (2014-2019), linked residential-address concentrations of NO 2 and PM 2.5 to individual-level hospital and mortality data. To evaluate incident ischemic stroke, we created a cohort of residents ≥30 years and free of ischemic stroke at baseline and for incident IHD we created a cohort free of IHD. We performed Cox proportional hazard survival analyses in each cohort with 2014 average concentrations of PM 2.5 or NO 2 as determinants, stratified by ethnicity (Dutch, German, Indonesian, Surinamese, Moroccan, Turkish) and adjusted for age, sex, socioeconomic indicators and region. RESULTS: Both cohorts included > 9.5 million people. During follow-up, 127,673 (1.3%) developed ischemic stroke and 156,517 (1.6%) developed IHD. For ischemic stroke, the p-values for the interaction between air pollution and ethnicity were 0.057 for NO 2 and 0.055 for PM 2.5. The HR of 1 IQR increase (6.42 µg/m 3) of NO 2 for ischemic stroke was lowest for Moroccans (0.92 [0.84-1.02], p-value = 0.032 difference with Dutch) and highest for Turks (1.09 [1.00-1.18], p-value = 0.157 difference with Dutch). PM 2.5 results were similar. For IHD, higher exposure was unexpectedly associated with lower incidence. The p-values for the interaction with ethnicity were 1.75*10 - 5 for NO 2 and 1.06*10 - 3 for PM 2.5. The HRs for IHD were lowest for Turks (NO 2: 0.88 [0.83-0.92], p-value = 2.0*10 - 4 difference with Dutch, PM 2.5: 0.86 [0.82-0.91], p-value = 1.3*10 - 4 difference with Dutch) and highest for Surinamese (NO 2: 1.02 [0.97-1.07], p-value = 0.014 difference with Dutch) and Dutch (PM 2.5: 0.96 [0.94-0.98]). CONCLUSIONS: Associations between air pollutants and ischemic stroke or IHD differ notably between ethnic groups in the Netherlands. Policies to reduce air pollution and prevent ischemic stroke should target populations vulnerable to air pollution with a high cardiovascular disease risk.