Vitamin D Deficiency Is Associated With An Increased Risk of Diabetes In Older Irish Adults: Results From The TUDA Study

Background Several studies have shown that vitamin D deficiency may increase the risk of developing type II diabetes and prediabetes. However, the data are inconsistent. Vitamin D may improve insulin sensitivity and pancreatic beta cell function, which could influence diabetes risk. We aimed to examine the relationship between vitamin D deficiency and type II diabetes in older Irish adults. Methods Study participants were from a cross-sectional study of adults aged > 60 years; Trinity Ulster University Department of Agriculture (TUDA) study. Diabetes was defined by self-report, use of diabetic medications or HBA1c ≥ 6.5%. Vitamin D deficiency was defined as 25(OH)D < 30 nmol/l. The relationship between vitamin D deficiency and diabetes was explored in multivariate logistic regression adjusting for age, sex, BMI, waist hip ratio, season, vitamin D supplement use, timed up and go, alcohol intake, current or previous steroid use, smoking, use of statins and socioeconomic status. Results There were 5171 participants (67.2% female, mean age 74.0 years) of whom 19.7% were vitamin D deficient and 15.7% had diabetes. Vitamin D deficiency versus non-deficiency was associated with an increased risk of diabetes both before and after multivariate adjustment (OR 1.46, 1.98-1.79, p<0.0002). Conclusion Vitamin D deficiency was associated with a 46% increased risk of having type II diabetes. However, the results of longitudinal studies and randomised trials have produced inconsistent results, though many had participants with higher baseline 25(OH)D status. A recent review of 46 trials of vitamin D supplementation found that it may reduce Hba1c in diabetics with vitamin D deficiency. Well designed trials to assess the potential effect of vitamin D supplementation on diabetic risk should be conducted.