Exposure to pesticides is associated with a 61% increased risk for developing diabetes, results of a new meta-analysis suggest.
The data, which were presented at EASD 2015, the annual meeting of the European Association for the Study of Diabetes, also indicate that different types of pesticides may pose a greater risk than others.
How diabetes develops is considered to be an interplay between genetic and environmental factors. Emerging evidence suggests that environmental contaminants, including pesticides, may play an important role in the pathogenesis of diabetes.
In this study, the researchers performed a systematic review and meta-analysis of observational studies that assessed the association between exposure to pesticides and diabetes. The association between exposure to any pesticide and all types of diabetes was examined. In addition, the researchers conducted a separate analysis for studies that looked only at type 2 diabetes.
“We were not surprised by our findings but, in most of the cases, similar findings are inflated, biased or simply not true. However, we were surprised by the consistency of the results in different subgroup and sensitivity analyses where the relative risk remains high,” said study co-author Evangelos Evangelou, MSc, PhD, from the University of Ioannina School of Medicine in Greece and the Imperial College London in the United Kingdom.
The researchers identified 21 studies assessing the association between pesticides and diabetes, covering 66,714 individuals. There were a total of 5,066 cases and 61,648 controls.
Most of the studies did not report the specific diabetes type examined, and in almost all of the studies analyzed, pesticide exposure was determined by blood or urine biomarker analysis.
Results revealed that exposure to any type of pesticide was associated with a 61% increased risk for any type of diabetes. In the 12 studies analyzing only type 2 diabetes, the risk was increased by 64% for those exposed to pesticides.
For individual pesticides, increased risk was identified in association with exposure to chlordane, oxychlordane, trans-nonachlor, DDT, DDE, dieldrin, heptachlor and HCB.
“Organic contaminants may play a role in the pathogenesis of diabetes. Of course, diabetes has a clear genetic background and also age and obesity are strong risk factors. Exposure to pesticides or possible interactions with other known genetic or environmental risk factors may play a role in the risk of type 2 diabetes,” Evangelou told Endocrinology Advisor.
“It is of interest how they (pesticides) are continuously released from fat stores to the blood and reach critical organs.”
Subgroup analyses did not reveal any differences in the risk estimates based on the type of studies or the measurement of the exposure. However, the researchers found that by analyzing each pesticide separately, some pesticides appeared to be more likely to contribute to the development of diabetes compared with others.
The results need to be interpreted with caution due to the observational nature of the data, the researchers noted. Currently, they are performing additional analyses of the data and doing a further meta-analysis of pesticide exposure in relation to other outcomes, including neurological outcomes and several cancers.
“We should always keep in mind that the current evidence derives from observational studies where recall and other biases may inflate the observed effect sizes,” said Evangelou.
“Our findings are supported by mechanistic studies and are scientifically interesting regarding the mechanisms underlying the linkage of pesticides and their mode of action with type 2 diabetes.”
Evangelou said most of the examined pesticides in the current analyses were banned a few decades ago in Western countries, and their levels are decreasing compared with earlier years. However, Evangelou and colleagues believe this an important area of research due to the worldwide epidemic of diabetes.
Further studies are warranted to better elucidate the association between pesticide exposure and the development of diabetes, Evangelou.
- Ntritsos G et al. Abstract 310: Association between diabetes and exposure to pesticides: a systematic review and meta-analysis. Presented at: EASD 2015; Sept. 15-18, 2015; Stockholm.