Journal Article

An Environment-Wide Association Study (EWAS) on Type 2 Diabetes Mellitus

Bhattacharya, Jayanta, Patel, Chirag J., Butte, Atul J.

2010

Overview

Type 2 Diabetes (T2D) and other chronic diseases are caused by a complex combination of many genetic and environmental factors. Few methods are available to comprehensively associate specific physical environmental factors with disease. We conducted a pilot Environmental-Wide Association Study (EWAS), in which epidemiological data are comprehensively and systematically interpreted in a manner analogous to a Genome Wide Association Study (GWAS). We performed multiple cross-sectional analyses associating 266 unique environmental factors with clinical status for T2D defined by fasting blood sugar (FBG) concentration > or =126 mg/dL. We utilized available Centers for Disease Control (CDC) National Health and Nutrition Examination Survey (NHANES) cohorts from years 1999 to 2006. Within cohort sample numbers ranged from 503 to 3,318. Logistic regression models were adjusted for age, sex, body mass index (BMI), ethnicity, and an estimate of socioeconomic status (SES). As in GWAS, multiple comparisons were controlled and significant findings were validated with other cohorts. We discovered significant associations for the pesticide-derivative heptachlor epoxide (adjusted OR in three combined cohorts of 1.7 for a 1 SD change in exposure amount; p<0.001), and the vitamin gamma-tocopherol (adjusted OR 1.5; p<0.001). Higher concentrations of polychlorinated biphenyls (PCBs) such as PCB170 (adjusted OR 2.2; p<0.001) were also found. Protective factors associated with T2D included beta-carotenes (adjusted OR 0.6; p<0.001). Despite difficulty in ascertaining causality, the potential for novel factors of large effect associated with T2D justify the use of EWAS to create hypotheses regarding the broad contribution of the environment to disease. Even in this study based on prior collected epidemiological measures, environmental factors can be found with effect sizes comparable to the best loci yet found by GWAS.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Analysis / Blood glucose / Blood levels / Body mass / Body mass index / Body size / Carotenoids / Carotenoids - blood / Chlorinated solvents / Chronic diseases / Chronic illnesses / Cohort Studies / Consortia / Diabetes / Diabetes and Endocrinology/Type 2 Diabetes / Diabetes mellitus / Diabetes mellitus (non-insulin dependent) / Diabetes Mellitus, Type 2 - blood / Disease control / Environment / Environmental factors / Environmental health / Epidemiology / gamma-Tocopherol - blood / Genetics / Genetics and Genomics/Bioinformatics / Genetics, Population / Genome-wide association studies / Genomes / Genomics / Health Surveys / Heptachlor / Heptachlor epoxide / Humans / Hypotheses / Informatics / Medical laboratories / Medical research / Medicine / Minority & ethnic groups / Nutrition / Obesity / PCB / PCB compounds / Pediatrics / Pesticides / Pesticides - blood / Pollutants / Polychlorinated biphenyls / Polychlorinated Biphenyls - blood / Public Health and Epidemiology/Environmental Health / Regression analysis / Regression models / Reproducibility of Results / Socioeconomics / Studies / Sugar / Tocopherol / Tocopherols / Type 2 diabetes / Working groups