title: Exposure to pesticides and diabetes: A systematic review and meta-analysis.
abstract: BACKGROUND
  Diabetes mellitus has a multifactorial pathogenesis with a strong genetic component as well as many environmental and lifestyle influences. Emerging evidence suggests that environmental contaminants, including pesticides, might play an important role in the pathogenesis of diabetes.
  
  
  OBJECTIVE
  We performed a systematic review and meta-analysis of observational studies that assessed the association between exposure to pesticides and diabetes and we examined the presence of heterogeneity and biases across available studies.
  
  
  METHODS
  A comprehensive literature search of peer-reviewed original research pertaining to pesticide exposure and diabetes, published until 30st May 2015, with no language restriction, was conducted. Eligible studies were those that investigated potential associations between pesticides and diabetes without restrictions on diabetes type. We included cohort studies, case-control studies and cross-sectional studies. We extracted information on study characteristics, type of pesticide assessed, exposure assessment, outcome definition, effect estimate and sample size.
  
  
  RESULTS
  We identified 22 studies assessing the association between pesticides and diabetes. The summary OR for the association of top vs. bottom tertile of exposure to any type of pesticide and diabetes was 1.58 (95% CI: 1.32-1.90, p=1.21×10(-6)), with large heterogeneity (I(2)=66.8%). Studies evaluating Type 2 diabetes in particular (n=13 studies), showed a similar summary effect comparing top vs. bottom tertiles of exposure: 1.61 (95% CI 1.37-1.88, p=3.51×10(-9)) with no heterogeneity (I(2)=0%). Analysis by type of pesticide yielded an increased risk of diabetes for DDE, heptachlor, HCB, DDT, and trans-nonachlor or chlordane.
  
  
  CONCLUSIONS
  The epidemiological evidence, supported by mechanistic studies, suggests an association between exposure to organochlorine pesticides and Type 2 diabetes.
authors.affiliation: Department of Hygiene and Epidemiology, University of Ioannina Medical School, Ioannina, Greece; Department of Biostatistics and Epidemiology, Imperial College London, London, UK.
authors.forename: Evangelos
authors.initials: E
authors.lastname: Evangelou
authors.affiliation: Department of Hygiene and Epidemiology, University of Ioannina Medical School, Ioannina, Greece.
authors.forename: Georgios
authors.initials: G
authors.lastname: Ntritsos
authors.affiliation: Department of Hygiene and Epidemiology, University of Ioannina Medical School, Ioannina, Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Chondrogiorgi
authors.affiliation: Oxford Centre for Diabetes, Endocrinology & Metabolism, University of Oxford, Churchill Hospital, Oxford, UK.
authors.forename: Fotini K
authors.initials: FK
authors.lastname: Kavvoura
authors.affiliation: University of Granada, School of Medicine, Granada, Spain.
authors.forename: Antonio F
authors.initials: AF
authors.lastname: Hernández
authors.affiliation: Department of Hygiene and Epidemiology, University of Ioannina Medical School, Ioannina, Greece.
authors.forename: Evangelia E
authors.initials: EE
authors.lastname: Ntzani
authors.affiliation: Department of Hygiene and Epidemiology, University of Ioannina Medical School, Ioannina, Greece; Department of Biostatistics and Epidemiology, Imperial College London, London, UK; MRC-PHE Centre for Environment and Health, Imperial College London, UK. Electronic address: i.tzoulaki@imperial.ac.uk.
authors.forename: Ioanna
authors.initials: I
authors.lastname: Tzoulaki
mesh_terms: D016022:Case-Control Studies; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology*; D004781:Environmental Exposure / Q000032:analysis*; D004785:Environmental Pollutants / Q000032:analysis*; D006801:Humans; D006843:Hydrocarbons, Chlorinated / Q000032:analysis*; D010575:Pesticides / Q000032:analysis*
chemical_list: D004785:Environmental Pollutants; D006843:Hydrocarbons, Chlorinated; D010575:Pesticides
keywords: Diabetes mellitus; Heterogeneity; Meta-analysis; Organochlorines; Pesticides; Type 2 diabetes