Association of vitamin D deficiency and chronic kidney disease in comorbid patients with type 2 diabetes mellitus

Introduction. The combination of type 2 diabetes mellitus (T2DM) and chronic kidney disease (CKD) worsens the patient’s prognosis. Vitamin D deficiency, which is involved not only in the regulation of calcium metabolism but also in immune and anti-inflammatory processes, may accelerate the development of CKD in patients with T2DM. Aim. To assess the association between vitamin D deficiency and the presence of CKD and to determine the threshold value of vitamin D levels associated with the presence of CKD in comorbid patients with T2DM. Materials and methods. Participants: 172 patients with type 2 diabetes mellitus aged 47 to 85 years (mean age 67.36 years). The examination included the collection of complaints, measurement of blood pressure, anthropometry and laboratory diagnostics (blood and urine tests, vitamin D [25(OH)D] levels, GFR). Patients with T2DM were classified according to vitamin D levels (25(OH)D) into four subgroups: normal level (30–60 ng/ml), insufficiency (20–29 ng/ml), deficiency (10–19 ng/ml), pronounced deficiency (less than 10 ng/ml). The diagnosis of CKD was based on the KDIGO criteria. Results. In patients with T2DM and CKD, vitamin D levels were significantly lower: median 17.0 ng/ml vs. 42.0 ng/ml in patients without CKD (p < 0.001). Vitamin D deficiency maintained an independent inverse association with CKD after adjustment for obesity and duration of T2DM (adjusted odds ratio 0.570; 95% CI: 0.424–0.767; p < 0.001). The optimal threshold value of vitamin D for detecting CKD is 27 ng/ml (sensitivity – 96.3 %, specificity – 84.2 %, AUC – 0.953). Conclusion. The analysis revealed a pattern: in patients with T2DM, vitamin D deficiency is associated with a higher frequency of CKD detection, which allows this indicator to be considered as an early signal of potential nephrological risk. Its measurement can become part of the standard screening to identify individuals at high risk of CKD.