Vitamin D affects the neutrophil‐to‐lymphocyte ratio in patients with type 2 diabetes mellitus

AIMS/INTRODUCTION: Chronic inflammation is an underlying feature of type 2 diabetes mellitus. Hypovitaminosis D is associated with type 2 diabetes mellitus, but whether it contributes to chronic inflammation is unclear. We examined the effects of vitamin D on various immune markers to evaluate its contribution to systemic inflammation in type 2 diabetes mellitus. MATERIALS AND METHODS: We retrospectively analyzed data from type 2 diabetes mellitus patients, people with prediabetes and control patients without diabetes (n = 9,746). Demographic and clinical variables were evaluated using descriptive statistics and generalized linear regression. A stratified analysis based on total serum vitamin D was also carried out. RESULTS: Neutrophil count was a significant predictor of 1,5‐anhydroglucitol and glycated hemoglobin (HbA1c) in patients with prediabetes (1,5‐anhydroglucitol: β = −0.719, P < 0.001 and HbA1c: β = −0.006, P = 0.002) and patients with diabetes (1,5‐anhydroglucitol: β = 0.207, P = 0.004 and HbA1c: β = −0.067, P = 0.010). Lymphocyte count was a significant predictor of HbA1c in patients without diabetes (β = 0.056, P < 0.001) and patients with prediabetes (β = 0.038, P < 0.001). The neutrophil‐to‐lymphocyte ratio (NLR) was a significant predictor of HbA1c in patients without diabetes (β = −0.001, P = 0.032). No immune markers differed significantly based on vitamin D level among patients without diabetes (P> 0.05 for all). Among patients with prediabetes, those who were vitamin D‐deficient had the highest NLR (P = 0.040). Among patients with diabetes, those who were vitamin D‐deficient had the highest neutrophil count (P = 0.001), lowest lymphocyte count (P = 0.016) and highest NLR (P < 0.001). CONCLUSIONS: The NLR is strongly influenced by serum vitamin D level. Given the high prevalence of hypovitaminosis D and elevated NLR among chronic disease patients and the elderly, our results suggest that clinical interpretation of NLR as a predictive marker of type 2 diabetes mellitus‐related inflammation should consider vitamin D level, age and pre‐existing morbidity.