Association between vitamin D status and metabolic syndrome in a longitudinal study of Iranian adults

Abstract

Background In recent years, hypovitaminosis D has been linked to many chronic diseases, including metabolic syndrome (MetS). However, there are considerable discrepancies in the study findings. Therefore, the present study investigated the association between vitamin D status and MetS in a cohort of Iranian adults followed from 2001 to 2013. Method This study was designed using the data from Isfahan cohort study which is an ongoing cohort of Iranian adults. For this study, 170 cases with MetS were selected from those who were free of MetS in 2001 but developed the condition in 2013. Controls (n=200) were selected from those who were free of MetS throughout the study period. Various biochemical parameters, including serum vitamin D concentrations, and socio-demographic information were assessed in 2001, 2007 and 2013. Generalized Estimating Equations was used to analyse the longitudinal association between vitamin D status and MetS. Results The subjects with MetS had higher levels of serum vitamin D [25(OH)D], total cholesterol, triglyceride, body mass index, waist circumference, systolic and diastolic blood pressure than that in the control subjects in 2001, while they had lower physical activity levels. A family history of hyperlipidemia was also more prevalent in the subjects with MetS. This study did not find any association between MetS and serum vitamin D status after controlling for potential confounders. Conclusion In spite of the high prevalence of vitamin D deficiency and MetS among studied population, this study failed to show any association between vitamin D status and MetS and/or its components. Randomized controlled trials are warranted to investigate the potential association more meticulously.