Contribution of obesity as an effect regulator to an association between serum leptin and incident metabolic syndrome

Background: We investigated whether serum leptin can be a predictor for incident cases of MetS in a population-based study. Methods: This is a prospective cohort study of 1590 adults aged between 40 and 70 years, who did not have MetS in 2005–2008 (at baseline) and 2008–2011 (follow-up). The baseline serum leptin concentrations were measured by radioimmunoassay. Results: During an average of 2.8 years of follow-up, 113 men (17.1%) and 148 women (15.9%) developed MetS. In multivariable adjusted models, the odds ratio of incident MetS when comparing the lowest to the highest quartiles of leptin levels was 3.17 in men and 2.79 in women; nevertheless, the significance disappeared after adjusting for the body mass index (BMI). In subsidiary analyses by BMI, logistic regression analysis showed that subjects with the highest tertile of serum leptin level were 3.04 and 2.12 times more likely to have MetS than those with the lowest tertile in lean subjects (OR 3.04; 95% CI 1.44–6.41; p = .004 in men vs. OR 2.12; 95% CI 1.06–4.25; p = .036 in women, respectively). Conclusions: Obesity is an effect regulator, which can predict an association between increased serum leptin level and the incidence of MetS in lean subjects.