Oxidative stress and subclinical atherosclerosis in agricultural workers : a nested case control study

Abstract

Background and objectivesNumerous studies examining the complex pathophysiological mechanisms underlying cardiovascular events have revealed that oxidative stress plays a critical role in atherogenesis. The aim of this study was to investigate the association between oxidative stress and carotid artery intima-media thickness (CIMT) as an indicator of subclinical atherosclerosis in agricultural workers.Subjects and methods We identified 51 case participants (CIMT level ≥ 0.9 mm) who were enrolled during a visit to any cohort center between May 1, 2011, and August 31, 2011, and who had never had a cardiovascular event such as angina, myocardial infarction, or stroke. We randomly recruited 51 control participants (CIMT level < 0.9 mm) during the same period using frequency matching by age group. For oxidative stress markers, we measured the levels of 8-hydroxy 2′-deoxyquuanosine (8-OHdG), malondialdehyde (MDA), and 8-iso-prostaglandin F2α (isoprostane). To assess pesticide exposure, we calculated the lifetime exposure to pesticides in months. Conditional logistic regression models were used to evaluate the relative relationships between occupational history and oxidative stress markers in the presence of subclinical atherosclerosis.ResultsCompared with general workers and low oxidative stress strata, agricultural workers and high oxidative stress strata showed an overwhelmingly increased risk and odds ratios (ORs) of subclinical atherosclerosis beyond the sum of the ORs for the other strata (OR [95% confidence interval], 16.00 [3.99–64.18] for isoprostane, 10.40 [3.07–35.28] for MDA, and 8.64 [2.57–29.07] for 8-OHdG). In path analysis, pesticide exposure had a direct effect on the increase of oxidative stress levels (β = 0.425 for isoprostane, β = 0.396 for MDA, and β = 0.264 for 8-OHdG) and an indirect effect on CIMT (β = 0.146 for model A and β = 0.161 for model B). Oxidative stress had a direct effect on CIMT (β = 0.248 for isoprostane, β = 0.227 for MDA, and β = 0.328 or 0.330 for 8-OHdG).ConclusionWe observed an increased risk of developing subclinical atherosclerosis in agricultural workers who had higher levels of oxidative stress than general workers. In addition, the higher levels of oxidative stress were correlated with pesticide exposure. The deducible pathologic links between agricultural workers and their higher risk of subclinical atherosclerosis could be explained by the indirect effect of pesticide exposure on oxidative stress levels.