The association of serum 25-hydroxyvitamin D and vertebral fractures in patients with type 2 diabetes

Vitamin D is an important regulator of bone health. Previous studies examining the association between vitamin D deficiency and osteoporotic fractures have reported conflicting results. The relationship between vitamin D status and risk of vertebral fractures in diabetic patients is unknown. The objective of this study was to examine whether low serum 25-hydroxyvitamin D [25(OH)D] levels were associated with vertebral fractures in patients with type 2 diabetes. This cross-sectional study was conducted among 161 postmenopausal women and 180 men with type 2 diabetes. Serum concentrations of 25(OH)D were measured and the presence of vertebral fracture was assessed using lateral plain radiographs of the thoracolumbar spine. Women had lower 25(OH)D levels than men (31.3 +/- 17.7 vs. 41.3 +/- 26.5 ng/mL, p<0.001). Vertebral fractures were found in 16% of patients. Men with a serum 25(OH)D concentration greater than 30 ng/mL showed a lower prevalence of vertebral fractures compared to those with 20-29.9 ng/mL or those with less than 20 ng/mL (9.4% vs. 17.9% vs. 21.7%, p for trend=0.036). However, there was no significant association between vitamin D status and the prevalence of vertebral fractures in women (14.4% vs. 19.2% vs. 26.6%, p for trend=0.111). After adjusting for multiple confounding factors, men with a serum 25(OH)D concentration of less than 20 ng/mL were associated with an increased risk of vertebral fractures (OR 7.87; 95% CI 1.69-36.71), but not women. In conclusion, serum 25(OH)D levels below 20 ng/mL were associated with an increased vertebral fracture risk in men with type 2 diabetes.