Is Vitamin D Status a Factor Influencing the Onset of Neuropathy in Type 2 Diabetics?

Introduction: A growing body of evidence suggests that the role of vitamin D (vit D) is not limited to phosphocalcic homeostasis, but other target organs have also been discovered, justifying a growing interest in this hormone. Although a drop in vit D levels is very common in type 2 diabetes mellitus (T2DM), no study has shown that this is a major factor in the onset of diabetic neuropathy. The aim of this study was to determine the prevalence of vit D deficiency in patients with T2DM, to identify factors influencing vit D status and to study the association between vit D deficiency and the development of neuropathy in patients with type T2DM. Methods: A cross-sectional study was conducted at the Farhat Hached University Hospital Centre (CHU) in Sousse, among type 2 diabetic patients aged between 25 and 70 years. All patients presenting a physiological or pathological situation likely to lead to hypovitaminosis D were excluded. Results: A total of 155 patients were included. There were 62 men (40%) and 93 women (60%), giving a sex ratio of 0.66. Nearly 2/3 (64%) were over 50 years of age, with a mean age of 53.4±10.8 years. Diabetic peripheral neuropathy was diagnosed in 40% (62 patients) of cases with a mean DN4 score of 2.8 ± 2.67. The most common vegetative neuropathy was cardiovascular autonomic neuropathy (29.23%), followed by gastrointestinal digestive neuropathy (26.15%). Only one patient with neuropathy had normal vitamin status and almost all (60 patients) had vit D levels below 20 ng/ml. The mean vit D level was significantly lower in diabetics with neuropathy than in those without this complication (p≤ 10-3). There was a statistically significant negative correlation between mean vit D level and DN4 score (p=10-3). The univariate study showed that a vit D level < 20 ng/ml was one of the factors associated with the onset of neuropathy (p=10-3). After multiple binary logistic regression, including the variables of interest, vit D level appeared to be significantly associated with neuropathy (p=0.012) with an adjusted OR=0.904. Conclusion: Our results show that vit D deficiency is a risk factor directly and independently associated with the development of peripheral neuropathy.