In a recent study published in Environment International, “Serum mercury concentration and the risk of ischemic stroke: The Reasons for Geographic and Racial Differences in Stroke Trace Element Study,” a team of IU School of Public Health-Bloomington researchers, led by Cheng Chen, examined the association between serum mercury levels with the incidence of ischemic stroke and to explore the possible effect modifications by serum selenium levels and demographic and geographic factors.
Although biologically plausible, epidemiological evidence linking exposure to methylmercury with an increased risk of ischemic stroke is limited. The effects of methylmercury may be modified by selenium, which is an anti-oxidant that often co-exists with mercury in fish.
The team (which included Pengcheng Xun, Leslie A. McClure, John Brockman, Leslie MacDonald, Mary Cushman, Jianwen Cai, Lisa Kamendulis, Jason Mackey, and Ka He) found no statistically significant association was observed between serum mercury concentration and the incidence of ischemic stroke (the highest vs. lowest quintile of mercury levels: HR = 0.82; 95% CI = 0.55-1.22; P for linear trend = 0.42). Sex (P for interaction = 0.06), but not serum selenium levels, modified the association; a more evident trend toward lower incidence of ischemic stroke with higher mercury levels was observed among women.
The findings of this study do not support an association between mercury and the incidence of ischemic stroke in a US population with low-to-moderate levels of exposure. Selenium levels did not modify the association. However, environmental contamination of mercury should be continuously monitored and controlled since mercury still has the potential to counteract the cardiovascular benefits of fish consumption.