Mercury Exposure, Blood Pressure, and Hypertension: A Systematic Review and Dose response Meta-analysis

BACKGROUND: Body burden of mercury has been linked to hypertension in populations exposed to high mercury levels. OBJECTIVES: We summarized, extracted, and pooled the results of published studies that investigated mercury biomarkers and hypertension or blood pressure (BP) measurements to examine this potential relationship. METHODS: We searched PubMed, Embase, and TOXLINE and selected studies according to a priori defined inclusion criteria. Study quality was assessed by the Newcastle-Ottawa scale for cohort and case-control studies and the Quality Assessment Tool for cross-sectional studies. Study estimates were pooled using inverse-variance weighted random-effects models. Dose-response meta-analysis was performed with studies reporting hypertension and systolic BP for at least three mercury categories. RESULTS: A total of 29 studies were included in the meta-analysis. The pooled odds ratio (OR) for hypertension, comparing the highest and lowest mercury exposure categories, was 1.35 [95% confidence interval (CI): 0.99, 1.83] for populations with hair mercury <= 2 mu g/g in comparison with the OR of 1.12 (95% CI: 0.82, 1.52) for populations with hair mercury <2 mu g/g. Positive associations were also observed for highest versus lowest mercury exposure categories on systolic and diastolic BP. Heterogeneity was observed for mercury species and exposure groups across different studies. Associations estimated using different mercury biomarkers generally agree with each other in the same study. A nonlinear dose-response relationship with an inflection point at 3 mu g/g was identified, for both hypertension and systolic BP. CONCLUSIONS: A significant positive association between mercury and hypertension and between mercury and BP was identified. The exposure dose is an important factor in determining the toxic effects of mercury on hypertension.