Association of low to moderate levels of arsenic exposure with risk of type 2 diabetes in Bangladesh

Abstract

Chronic exposure to high levels of arsenic in drinking water is associated with increased risk of type 2 diabetes mellitus (T2DM), but the association between lower levels of arsenic and T2DM is more controversial. Therefore, this study evaluated the association between low to moderate arsenic exposure and T2DM. In 2009-2011, we conducted a study of 957 Bangladeshi adults who participated in a case-control study of skin lesions in 2001-2003. The odds ratio of T2DM was evaluated in relationship to arsenic exposure measured in drinking water and in subjects' toenails (in 2001-2003) prior to the diagnosis of T2DM (in 2009-2011). Compared with those exposed to the lowest quartile of arsenic in water (≤ 1.7 µg/L), the adjusted odds ratio for T2DM was 1.92 (95% confidence interval (CI): 0.82, 4.35) for those in the second quartile, 3.07 (95% CI: 1.38, 6.85) for those in the third quartile, and 4.51 (95% CI: 2.01, 10.09) for those in the fourth quartile. The relative excess risk of T2DM was 4.78 for individuals who smoked and 8.93 for people who had a body mass index (weight (kg)/height (m)(2)) greater than 25. These findings suggest that exposure to modest levels of arsenic in drinking water was associated with increased risk of T2DM in Bangladesh. Being overweight or smoking was also associated with increased risk of T2DM.

Keywords: Bangladesh; additive interaction; arsenic; diabetes; overweight; smoking.

Figure 1.

Dose-response curve between arsenic exposure and change in risk of type 2 diabetes mellitus among residents exposed to arsenic in drinking water at levels less than 170 μg/L in Pabna, Bangladesh, 2001–2011. Associations are shown for A) type 2 diabetes and arsenic in drinking water and C) toenail arsenic. Restricted analyses of dose-response curves on residents without skin lesions at baseline (in 2001–2003) are shown for B) type 2 diabetes and arsenic in drinking water and D) toenail arsenic. The odds ratios were estimated by penalized splines with the reference value set at the lowest exposure levels of arsenic in drinking water (0.5 μg/L, based on samples whose values were lower than the limit of detection) or toenail arsenic (<0.11 μg/g). Odds ratios were adjusted for age, sex, body mass index (BMI) (weight (kg)/height (m)²), cigarette smoking, and skin lesions for A and C. Odds ratios were adjusted for age, sex, BMI, and cigarette smoking for B and D. There were 709 subjects whose exposures to arsenic in drinking water were below 170 μg/L (A and C) and 354 subjects whose exposures to arsenic in drinking water were below 170 μg/L and who were without skin lesions at baseline (B and D). The P values of penalized splines were <0.001, 0.008, 0.017, and 0.043 for A, B, C, and D, respectively. Water and toenail arsenic levels were transformed into a natural logarithm scale. Solid lines denote the estimated odds ratios, and dashed lines denote the 95% confidence intervals of the odds ratios.