Absence of association between vitamin D deficiency and incident metabolic syndrome: Tehran Lipid and Glucose Study.

Background: Links between vitamin D status and metabolic syndrome have been reported in cross-sectional studies; however, few prospective studies regarding this association exist. We performed this study to assess prospective association between vitamin D status and incident metabolic syndrome in a large population-based cohort.

Method: This was a nested case-control study within the Tehran Lipid and Glucose Study (TLGS) which followed representative Tehranian adults. A total of 324 matched pairs aged 20 or older were selected. Cases and controls were free of metabolic syndrome according to definition of Joint Interim Statement (JIS) at baseline and followed for a mean duration of 6.8 years. Each case was matched individually by sex, age, duration of follow-up, and month of entry to the study with a randomly selected control. Prespecified cut points were used to characterize varying degrees of 25-hydroxyvitamin D [25(OH)D] deficiency (<20, 20-29.9, and ≥30 ng/mL). Conditional logistic regression was used to investigate the association between 25(OH)D concentration and the incident metabolic syndrome.

Results: The mean age of participants was 40.8±11.7, and 50% were women. The median [interquartile range (IQR) 25-75] of serum 25(OH) D was 16 ng/mL (10-25 ng/mL) and there was no difference between cases (16 ng/mL; IQR 10-25 ng/mL) and controls (16 ng/mL; IQR 10-26 ng/mL). The odds ratio of serum 25(OH)D <20 ng/mL for developing metabolic syndrome was 0.97 [95% confidence interval (CI) 0.6-1.52] compared with serum 25(OH)D ≥30 ng/mL. Adjustment for potential confounders did not change the results.

Conclusions: Our study does not provide evidence that there is association between different serum vitamin D levels and incidence of metabolic syndrome.