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Non‐linear association between 25‐hydroxyvitamin D and the incidence of Type 2 diabetes: a community‐based nested case–control study
Author(s) -
Tohidi M.,
Bozorgmanesh M.,
Mohebi R.,
Khalili D.,
Saadat N.,
Khorrami N.,
Azizi F.,
Hadaegh F.
Publication year - 2013
Publication title -
diabetic medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.474
H-Index - 145
eISSN - 1464-5491
pISSN - 0742-3071
DOI - 10.1111/dme.12180
Subject(s) - medicine , odds ratio , type 2 diabetes , diabetes mellitus , confidence interval , nested case control study , incidence (geometry) , body mass index , endocrinology , logistic regression , gastroenterology , physics , optics
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.