Even low to moderate levels of exposure to inorganic arsenic in food and water correlate with cardiovascular disease incidence and mortality, according to an analysis of the Strong Heart Study.
The results were published online Sept. 24 in Annals of Internal Medicine.
Katherine A. Moon
High environmental arsenic levels have long been recognized as correlating with higher risk of cardiovascular disease, but a secondary analysis of data from a large prospective heart study now shows that even at low levels commonly found in rural communities across the United States, arsenic exposure is strongly related to cardiovascular risk and mortality in a dose-dependent fashion.
"These findings support the importance of low to moderate arsenic exposure as a cardiovascular risk factor with no apparent threshold," said Katherine A. Moon of the department of environmental sciences, Johns Hopkins University Bloomberg School of Public Health, Baltimore, and her associates.
They assessed this correlation using data from the Strong Heart Study, a population-based cohort study of cardiovascular disease in three Native American communities in rural Arizona, Oklahoma, and the Dakotas. For their analysis, Ms. Moon and her colleagues measured arsenic species concentrations in stored urine samples from 3,575 men and women with no cardiovascular disease at enrollment during 1989-1991.
These study subjects, aged 45-75 years at baseline, were followed for cardiovascular outcomes for 17-19 years.
A total of 1,184 subjects developed cardiovascular disease during follow-up, with 846 incident coronary heart disease events and 264 incident strokes. A total of 439 subjects died from cardiovascular disease, including 341 who died from coronary heart disease and 54 who died from stroke.
Urinary arsenic concentrations at baseline correlated with the development of cardiovascular disease. Compared with men and women who had the lowest arsenic levels, those in the highest quartile were more likely to develop cardiovascular disease (hazard ratio 1.32), coronary heart disease (HR 1.30), and stroke (HR 1.47).
Urinary arsenic levels at baseline also correlated with cardiovascular mortality. Compared with men and women who had the lowest levels, those in the highest quartile were more likely to die from cardiovascular disease (hazard ratio, 1.65), coronary heart disease (HR, 1.71), or stroke (HR, 3.03).
These associations persisted after the data were adjusted to account for the effects of sociodemographic factors, smoking status, and lipid levels.
In contrast, urinary levels of arsenobetaine, an organic arsenical that is found chiefly in seafood and is thought to be nontoxic, showed no associations with cardiovascular outcomes.
Overall, these findings provide "important novel data in a Western population with high background cardiovascular risk," Ms. Moon and her associates noted.
The association between arsenic levels and cardiovascular risk was strongest among men and women who had diabetes, a subgroup of the population that has not been evaluated in previous studies of arsenic exposure. This finding "needs to be interpreted cautiously and requires replication in other populations," the researchers said.
The Environmental Protection Agency has estimated that 13 million Americans are chronically exposed to arsenic in drinking water, and many millions more are exposed to arsenic in food. It is possible that mitigating these exposures could reduce the burden of cardiovascular disease in the United States and across the globe, they added.
This study was supported by the National Heart, Lung, and Blood Institute and the National Institute of Environmental Health Sciences. No financial conflicts of interest were reported.