Association Between Vitamin D Levels and Glycemic Control Among Adult Diabetic Patients in Riyadh, Saudi Arabia

Background: Diabetes is one of the most common diseases worldwide. It can cause serious complications, such as cardiovascular events, end-stage renal disease, and blindness if not controlled. Vitamin D is believed to play an essential role in glucose metabolism and insulin resistance. However, few studies have been conducted in Saudi Arabia to confirm or reject this hypothesis. Thus, this study explored the relationship between vitamin D levels and glycemic control in a Saudi diabetic population. Materials and methods: This is a retrospective cohort study including all adults 18 years of age or older diagnosed with diabetes who underwent at least five years of regular follow-up at the family medicine clinic at the King Faisal Specialist Hospital (KFSH) from January 2015 to January 2021. Data were obtained from the patients' medical records and included detailed histories, physical examination records, and laboratory findings. Participants were divided into vitamin D deficiency and vitamin D sufficiency groups based on vitamin D levels. Results: A total of 370 patients with type 2 diabetes mellitus were enrolled in the study. The majority of the patients (60%) were over 65 years of age. The mean serum 25(OH) vitamin D level of the participants was 62.75 +/- 22.79 nmol/L. There was a significant association between glycemic control and vitamin D levels (p < 0.001). The mean level of vitamin D was higher in the good glycemic control group (70.96 +/- 22.66) than in the poor glycemic control group (54.81 +/- 19.98). A total of 13.74% (25) of the good glycemic control group had vitamin D levels < 50 nmol/L, while 52.13% (98) of the poor glycemic control had vitamin D levels < 50 nmol/L. Patients with poor glycemic control were 2.4 times more likely to have low vitamin D levels than patients in the well-controlled glycemic group. Conclusion: Based on the study results, serum vitamin D has a significant inverse relationship with HbA1c levels among diabetics. This finding highlights the need for routine screening of vitamin D status in all patients with diabetes and early treatment for those found to be deficient.