Arsenic exposure shown to be associated with type 2 diabetes prevalence

Low levels of exposure to inorganic arsenic in drinking water may be linked to the prevalence of type 2 diabetes among U.S. adults.

Researchers from Johns Hopkins Bloomberg School of Public Health in Maryland and other sites in Spain found that urine arsenic and dimethylarsinate levels were positively associated with elevated levels of glycated hemoglobin.

Using data from the NHANES study, the researchers conducted a cross-sectional study of 788 participants aged 20 years and older.

Diabetes prevalence was 7.7%. Overall, median urine levels were 7.1 mcg/L for arsenic, 3 mcg/L for dimethylarsinate and 0.9 mcg/L for arsenobetaine.

Participants with diabetes had a 26% higher level of arsenic than those without diabetes, after adjusting for seafood intake and diabetes risk factors (95% CI, 2%-56%). Compared to participants without diabetes, those with type 2 diabetes had a 10% higher level of dimethylarsinate, which the researchers reported as insignificant. Levels of arsenobetaine were similar in those with and those without diabetes.

Comparing participants at the 80th vs. 20th percentiles of urine arsenic, the OR for type 2 diabetes was 3.58 for arsenic (95% CI, 1.18-10.83), 1.57 for dimethylarsinate (95% CI, 0.89-2.76) and 0.69 for arsenobetaine (95% CI, 0.33-1.48). – by Stacey L. Adams

JAMA. 2008;300:814-822.

It occurs to me that there are two possible explanations for these findings: There may be a direct toxic effect of arsenic. The issue of a potential relationship of chronic diseases to environmental polutants is beginning to be explored, and may prove important as a mechanism of development of diabetes. Certainly there appears to be evidence that such toxicity may occur at high arsenic levels. Alternatively, levels of arsenic in drinking water might be, in some way, a proxy marker for social class. The authors of the study did find arsenic levels to be higher among participants who were black or Hispanic, in themselves risk factors for diabetes. When the researchers adjusted for sociodemographic and diabetes risk factors, participants with type 2 diabetes had similar levels of total arsenic and dimethylarsinate and lower levels of arsenobetaine than those without type 2 diabetes. Those who have more than high school education have lower arsenic levels and lower dimethylarsinate levels. It's not completely clear, then, that this is a direct effect.

– Zachary T. Bloomgarden, MD

Endocrine Today Editorial Board member