Association of Vitamin D Levels with Type 2 Diabetes in Older Working Adults

OBJECTIVES: Increasing evidence suggests that vitamin D plays a role in the development of chronic diseases including type 2 diabetes (DM). Aim of the study was to explore the association of vitamin D levels with prevalent DM in a sample of predominantly healthy working adults older than 45 years. METHODS: This cross-sectional study (2009-2011) involved 1821 employees of a German engineering company (83.1% male, mean age 51.9 +/- 5.6 years). Sociodemographics and medical history were assessed by self-report. Clinical characteristics were obtained including blood samples to determine vitamin D levels and diabetes status by fasting plasma glucose (FPG) and glycosylated hemoglobin (HbA1c). Vitamin D was grouped into one of four categories (<10 ng/ml, 10-19.9 ng/ml, 20-29.9 ng/ml, = 30 ng/ml). Bivariate associations between vitamin D categories and a composite indicator for DM (FPG >= 126 mg/dl or HbA1c >= 6.5% or self-reported diagnosis) were calculated; multivariable models tested this association further, controlling for potential confounders. RESULTS: Severe vitamin D deficiency (<10 ng/ml) was associated with increasing FPG (beta 3.13; 95% CI: 0.78, 5.47; p <= 0.01) and HbA1c (beta 0.15; 95% CI: 0.08, 0.23; p <= 0.001) values in adjusted linear regression models. In multivariable models, severe vitamin D deficiency was associated with DM (OR 2.55; 95% CI 1.16, 5.62; p <= 0.05) after controlling for potential confounders. CONCLUSIONS: Vitamin D deficiency is associated with prevalent DM in working older adults. The findings highlight that the workplace may be a unique location for conducting large-scale health screening to identify those at risk of DM using vitamin D.