Association between oxidative balance score and diabetes among PURE Poland study participants

Introduction Oxidative stress is caused by an imbalance between free radicals production and antioxidants activity. It plays an important role in the pathogenesis of diabetes mellitus (DM). The purpose of the study was to assess the relationship between oxidative balance score (OBS) and diabetes prevalence among PURE Poland study participants. Methods Study group included 1889 participants of the Polish arm of the Prospective Urban Rural Epidemiological (PURE) study (1185 women, 704 men), aged 35-70 years, from urban and rural area. The study was conducted in the first stage of the PURE Poland study. The study was approved by the Ethics Committee. Diabetes diagnosis was made based on fasting glucose level ≥ 126 mg/dl or declaration about DM occurrence in the medical interview. Impaired fasting glucose (IFG) was diagnosed when fasting glucose level was between 100-125 mg/dl with no statement about DM in the interview. Finally three analysis have been done: diabetes in the interview (DM_int), diabetes in the interview + diagnosis based on fasting glucose (DM_all) and DM_all + IFG (DM+IFG). Food intake was assessed using the Food Frequency Questionnaire (FFQ), which was developed and validated for this population within the PURE study. OBS was calculated taking into account prooxidant factors: smoking, BMI value, fats and iron intake with diet, and antioxidants intake with diet: zinc, copper, selenium, vitamin E and C, carotenoids, lycopene and flavonoids. The value of OBS was calculated by summing the points (from 0 to 2 for tertiles) for individual components. The maximum value of OBS could be 24 points, and higher number of points indicated better oxidative balance. Results Among women the prevalence of DM_int was 9.2%, 8.0% and 5.4% in the tertiles of OBS (T1, T2, T3, respectively). When comparing T3 vs T1 the odds ratio for DM_int prevalence was 0.56 (95% CI 0.33-0.96) for crude data, in model 2 with adjusting for energy intake 0.48 (95% CI 0.25-0.93) and in model 3 with adjusting for energy intake, age and place of residence 0.78 (95% CI 0.39-1.56). Taking into account DM_all among women there were no significant differences between OBS tertiles. The risk of DM+IFG prevalence among women was 34% lower (model 2; OR 0.66, 95% CI 0.47-0.94) in T3 vs T1 (31.9% vs 34.6%). Among men there were no significant differences between DM_int prevalence between OBS tertiles. DM_all prevalence was 14.6%, 12.3% and 8.5% in the tertiles of OBS, respectively. When comparing T3 vs T1 the OR for DM_all prevalence was 0.54 (95% CI 0.30-0.98) for crude data, 0.44 (95% CI 0.21-0.94) in model 2 and 0.59 (95% CI 0.27-1.29) in model 3. The risk of DM+IFG prevalence in the group of men was 63% lower (model 2; OR 0.47, 95% CI 0.29-0.77) in T3 vs T1 (31.0% vs 38.1%). Conclusions Higher value of the OBS meaning better oxidative balance, was associated with a lower risk of diabetes prevalence in the study group.