Elsevier

Environmental Research

Volume 123, May 2013, Pages 33-38
Environmental Research

A case-cohort study examining lifetime exposure to inorganic arsenic in drinking water and diabetes mellitus

https://doi.org/10.1016/j.envres.2013.02.005Get rights and content

Abstract

Background

Consumption of drinking water with high levels of inorganic arsenic (over 500 μg/L) has been associated with type II diabetes mellitus (DM), but previous studies have been inconclusive about risks at lower levels (<100 μg/L). We present a case-cohort study based on individual estimates of lifetime arsenic exposure to examine the relationship between chronic low-level arsenic exposure and risk of DM.

Methods

This case-cohort study included 141 cases of DM diagnosed between 1984 and 1998 as part of the prospective San Luis Valley Diabetes Study. A comparison sub-cohort of 488 participants was randomly sampled from 936 eligible participants who were disease free at baseline. Individual lifetime arsenic exposure estimates were determined using a methodology that incorporates the use of a structured interview to determine lifetime residence and employment history, geospatial modeling of arsenic concentrations in drinking water, and urine arsenic concentrations. A Cox proportional hazards model with known DM risk factors as time-dependent covariates was used to assess the association between lifetime exposure to inorganic arsenic in drinking water and incident DM.

Results

Our findings show a significant association between inorganic arsenic exposure and DM risk (hazard ratio [HR]=1.27, 95%=1.01, 1.59 per 15 μg/L) while adjusting for ethnicity and time varying covariates age, body mass index and physical activity level.

Conclusions

Exposure to low-level inorganic arsenic in drinking water is associated with increased risk for type II DM in this population based on a comprehensive lifetime exposure assessment.

Highlights

► We present complex lifetime exposure assessment for arsenic in drinking water. ► Our exposure assessment was validated with urinary biomarker. ► The risk for diabetes increases with exposure to arsenic in drinking water. ► The risk for diabetes with arsenic exposure is independent of known risk factors.

Section snippets

Background

Human exposure to arsenic can occur from many sources including the occupational setting (smeltering and wood preservation),, ingestion of contaminated food, and smoking; however, the majority of exposure is through drinking contaminated water (US EPA, 1988). Previous research has documented a relationship between exposure to high concentrations of inorganic arsenic in drinking water and the risk of type 2 diabetes mellitus (DM) (Lai et al., 1994, Tseng et al., 2000, Rahman et al., 2003, Wang

Study sample

The relationship between inorganic arsenic exposures over time and the risk of incident DM was studied using a case-cohort design within the San Luis Valley Diabetes Study (SLVDS). The SLVDS is a population-based prospective study of risk factors for diabetes mellitus (DM) and other related chronic diseases among Hispanic and non-Hispanic white residents of Alamosa and Conejos Counties in south-central Colorado who were 20 to 74 years of age at their initial study visit. Participant recruitment

Results

This study included a cohort of 548 participants in which there were 141 cases and 6956 person years of follow-up. The study cohort (n=488) was similar to the original cohort (n=936) in demographic, behavioral, and clinical characteristics. On average, cases were similar to non-cases in age and distribution of gender, income group, smokers, and intake of alcohol (Table 1). Cases had a higher percentage of Hispanics and participants with a family history of DM than non-cases. At baseline,

Discussion

In this case-cohort study we found a modest association between DM risk and lifetime exposure to low levels of inorganic arsenic in drinking water (<100 μg/L). Specifically, we found that for every 15 μg/L increase in arsenic concentration in the drinking water, risk for DM increased by 27 percent (95% CI 1% to 59%) after adjusting for ethnicity, and time varying measures of BMI and physical activity.

The cohort used for this study allowed for a strong study design because of the ongoing

Conclusion

Our study presents an association between chronic low-level inorganic arsenic exposure and DM while adjusting for known risk factors over time: age, BMI, ethnicity, and physical activity. Given the complexity of DM, future research relating arsenic exposure to intermediate endpoints is recommended. Investigating the association between inorganic arsenic and outcomes such as impaired glucose tolerance or insulin resistance can shed light on the mechanistic pathway for disease. Lastly, the

Funding

None.

Disclosure

We (authors) report no potential competing financial or non-financial interests.

Acknowledgments

The authors would like to thank Laurie-Peterson Wright and the chemistry laboratory staff at the Colorado Department of Public Health and Environment for their contribution to this research. We would also like to thank Dr. Richard Hamman for authorization to conduct this research as part of the San Luis Valley Diabetes Studies. We would like to thank all of the participants and residents of the San Luis Valley whose courtesy and interest in the research was the source of its success.

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