Background: Saudi Arabia has a high burden of diabetes mellitus and vitamin D deficiency. The objective of this study was to explore the association between glycosylated hemoglobin and 25-hydroxyvitamin D in patients with type 2 diabetes mellitus (T2DM) in Riyadh, Saudi Arabia.
Methods: An interview based cross-sectional study was conducted on 606 patients with type 2 diabetes, aged 30-75 years, visiting primary health care centers. Blood samples were collected for measuring HbA1c, 25(OH)D and bone and lipid markers. Multivariable linear regression analysis was conducted to explore the association between HbA1c and 25(OH)D.
Results: The mean (±SD) levels for HbA1c and 25(OH) D were 7.69 (±1.77) and 44.28 (±23.06), respectively. Around 55% of patients had uncontrolled HbA1c (>7.0), whereas vitamin D deficiency (<50 nmol/L) was found in 52.3% (=317). Multiple linear regression analysis found that a unit increase in vitamin D levels and parathyroid hormone levels was associated with -0.17 (-0.02, -0.01, p < 0.001) and -0.20 (-2.66, -1.18, p < 0.001) unit decrease in levels of HbA1c, respectively. Similarly, increasing age was associated with -0.15 (-0.01, -0.04, p = 0.002) unit decrease in HbA1c levels, whereas unit increases in serum alkaline phosphatase, calcium and diabetes duration were associated with 0.22 (0.01, 0.02, p < 0.001), 0.14 (1.03, 3.88, p = 0.001) and 0.26 (0.42, 0.78, p < 0.001) unit increase in HbA1c levels, respectively.
Conclusion: HbA1c levels are associated with 25-hydroxyvitamin D levels. For better control of HbA1c levels, it is important to maintain 25-hydroxyvitamin D level and bone markers within normal range.
Keywords: 25-hydroxyvitamin D; HbA1c; Saudi Arabia; Type 2 diabetes mellitus.