High selenium exposure lowers the odds ratios for hypertension, stroke, and myocardial infarction associated with mercury exposure among Inuit in Canada.

BACKGROUND: Selenium (Se) has been reported to protect against the neurotoxicity of mercury (Hg). However, the effect of Se against Hg on cardiovascular diseases remains unclear. Inuit living in the Arctic have high exposure to both Se and Hg through their marine mammal and fish rich traditional diet.

OBJECTIVE: To characterize the co-exposure of Hg and Se among Inuit in Canada and to assess the associations between Hg, Se and cardiovascular health outcomes, including stroke, hypertension, and myocardial infarction (MI).

METHODS: Data was collected from the International Polar Year Inuit Health Survey (IHS) conducted in 2007 and 2008. Blood Se and Hg were measured, and self-report cardiovascular health outcomes were collected through a questionnaire interview from 2169 adults aged 18 and above.

RESULTS: The mean age was 42.4years, and 38.7% of the participants were male. The geometric means (GM) of blood Se and total Hg were 319.5μg/L and 7.0μg/L, respectively. The crude prevalence of heart attack, stroke and hypertension were 3.55%, 2.36%, and 24.47% respectively. Participants were categorized into 4 exposure groups according to blood Hg (high: ≥7.8μg/L; low: <7.8μg/L), and Se (high: ≥280μg/L; low: <280μg/L). The odds ratio (OR) of cardiovascular outcomes were estimated using general linearized models. Results showed the low Se and high Hg group had a higher prevalence of cardiovascular disease (OR=1.76 for hypertension, 1.57 for stroke, and 1.26 for MI. However, the prevalence was decreased in both the high Se and low Hg group (OR=0.57 for hypertension, 0.44 for stroke, and 0.27 for MI) and the high Se and high Hg group (OR=1.14 for hypertension, 0.31 for stroke, and 0.80 for MI).

CONCLUSIONS: The high Se and low Hg group had the lowest prevalence of cardiovascular outcomes, except for stroke. These results provide evidence that Se may exhibit a protective effect against Hg on cardiovascular disease.