Environmental contaminant body burdens and the relationship with blood pressure measures among Indigenous Canadians

Abstract

OPS 18: Cardiometabolic effects of chemical exposures, Room 110, Floor 1, August 26, 2019, 1:30 PM - 3:00 PM Blood pressure (BP) increments increase cardiovascular disease (CVD) risk. Recently, clinical practice guidelines lowered hypertension definitions. Indigenous Canadians experience slightly higher CVD compared to non-Indigenous Canadians. Environmental contaminant body burden from persistent organochlorine pollutants, organic compound concentrations (OCs), and metals have been linked with hypertension risk. This study examined the role of OCs, and metals on hypertension among Indigenous Canadians. Methods: Using data from the Environment-and-Health Study in Eeyou Istchee territory of northern Québec, Canada, the sample restricted to adults over 20-years of age, with valid BP measures and detectable body burden mixtures. In total, n=774 participants were eligible, of which, n=452, 58% females. Principal Component Analysis (PCA) was used to reduce the complexity of the contaminant data. Orthogonal principal component (PC) variables were used as independent predictors in both multivariable linear regression, and modified Poisson regression models with robust variance estimation, deriving relative risk for hypertension defined using systolic BP (SBP) ≥140 mm Hg or diastolic BP (DBP) ≥90 mm Hg. Results: Three PCs were extracted from the PCA analysis. PC-1, PC-2, and PC-3, explained 72%, 5.5% and 4.8% of the variation, respectively. Polychlorinated biphenyls and OCs positively highly loaded on the first axes (PC-1), followed by moderate loadings for metal mercury. Lead loaded positively, whereas DDT negatively loaded on PC-2, and cadmium strongly loaded on the third PC axis. Systolic BP measures were significantly associated with PC-1 across all models. In the final model, PC-1 increased SBP β=1.72 (95% CI 0.42, 3.02). PC-3, represented by cadmium was associated with SBP but after adjusting for body mass, PC-3 was no longer associated with SBP. Hypertension was consistently and significantly associated with PC-1 across models, RR=1.14 (95% CI 1.02, 1.28) in the final adjusted model. Conclusion: Using a reduction technique, this cross-sectional analysis found OCs to be associated with increased SBP.