Non-linear association between 25-hydroxyvitamin D and the incidence of type 2 diabetes: A community-based nested case-control study

M. Tohidi, M. Bozorgmanesh, R. Mohebi, D. Khalili, N. Saadat, N. Khorrami, F. Azizi, F. Hadaegh

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18 Scopus citations


Aims: To examine the nature of the association between 25-hydroxyvitamin D [25(OH)D] and newly diagnosed type 2 diabetes. Methods: Serum 25(OH)D concentrations were measured for 761 participants (aged 20-83 years) in the Tehran Lipid and Glucose Study, selected for a 1-to-3 nested case-control study. Cases were 191 cases of Type 2 diabetes diagnosed during a median follow-up of 3.6 years. A total of 570 participants were matched with these cases with regard to age, sex, BMI, and month of entering the study. Diabetes was defined according to the American Diabetes Association criteria, 2003. Serum 25(OH)D was measured using the enzyme immunoassay method. Odds ratios for Type 2 diabetes were obtained from conditional logistic regression models for tertiles of serum 25(OH)D concentrations [tertile-1: 2.82-11.02 (reference), tertile-2: 11.03-21.80, and tertile-3: ≥ 21.82 ng/ml]. The multivariate model was adjusted for age, sex, family history of diabetes, systolic blood pressure, triglyceride-to- HDL cholesterol ratio, waist-to-height ratio, lifestyle modification intervention, leisure time physical activity, and fasting plasma glucose at baseline. Non-linearity in the associations between baseline 25(OH)D and Type 2 diabetes, was examined by using restricted cubic splines. Results: Unadjusted odds ratios (95% confidence intervals) of diabetes were 0.73 (0.74-1.13), 0.54 (0.34-0.85) for the second and third tertiles, respectively. Multivariate adjusted odds ratios were 0.47 (0.25-0.90) and 0.43 (0.23-0.82), respectively. Below the cutoff of ~ 10 ng/ml the risk of newly diagnosed Type 2 diabetes increased dramatically. Discussion: It was found that 25(OH)D concentrations contributed to the Type 2 diabetes incidence rate in a non-linear fashion, with the risk beginning to increase sharply for values < 10 ng/ml. What's new?: Few prospective studies, having measured baseline serum 25-hydroxyvitamin D [25(OH)D], have studied the association between vitamin D status and the risk of newly diagnosed Type 2 diabetes. Given the fact that 25(OH)D deficiency and Type 2 diabetes co-exist with a high prevalence among the Middle Eastern population, investigating if and how serum 25(OH)D concentrations contribute to the Type 2 diabetes incidence rate might be warranted. Using a community-based prospective study, we sought to examine the following: first, if serum 25(OH)D contributed to newly diagnosed Type 2 diabetes; and second, if a cutoff-point in the concentrations of 25(OH)D could be determined for identifying subjects at increased risk of Type 2 diabetes.

Original languageEnglish
Pages (from-to)934-938
Number of pages5
JournalDiabetic Medicine
Issue number8
StatePublished - Aug 2013
Externally publishedYes


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