Serum 25(OH)D and incident type 2 diabetes: a cohort study

BACKGROUND/OBJECTIVES: Mild to moderate vitamin D insufficiency has been proposed as a risk factor for several common chronic diseases including type 2 diabetes. This study aimed to examine the association between serum 25-hydroxy vitamin D (25(OH) D) and incident diabetes. SUBJECTS/METHODS: The MONICA10 cohort consists of 2656 participants (men and women aged 41-71 years) who participated in a 10-year follow-up examination during 1993-1994 as part of the MONICA 1 population survey. A total of 2571 participants free of diabetes at baseline and with successful measurement of serum 25(OH) D were included in the current study. The Danish National Diabetes register enabled identification of 288 cases of incident diabetes during follow-up (median: 16.4 years). Data were analysed by Cox proportional hazard models and associations were expressed as hazard ratios (HRs) with 95% confidence intervals (CIs). RESULTS: Serum 25(OH) D was inversely associated with incident diabetes adjusted for potential confounders (HR per 25 nmol/l=0.83; 95% CI: 0.72-0.95;P=0.009). A statistically significant interaction was observed between 25(OH) D and waist circumference (WC) (P-interaction=0.042) suggesting an association in persons with a high WC (HR (95% CI) per 25 nmol/l=0.74 (0.63-0.88), 218 incident cases) and not in persons with a normal WC (HR (95% CI) per 25 nmol/l=0.98 (0.78-1.24), 70 incident cases). CONCLUSIONS: Low serum 25(OH) D was associated independently with incident diabetes. The inverse association was only found in overweight-obese and not in normal weight individuals, suggesting that obesity may modify the effect of vitamin D status on the risk of diabetes. European Journal of Clinical Nutrition (2012) 66, 1309-1314; doi:10.1038/ejcn.2012.134; published online 3 October 2012