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TOPLINE:

Vitamin D deficiency is independently linked to the risk for diabetic peripheral neuropathy (DPN) by potentially affecting large nerve fibers in older patients with type 2 diabetes (T2D).

METHODOLOGY:

• Although previous research has shown that vitamin D deficiency is common in patients with diabetes and may increase the risk for peripheral neuropathy, its effects on large and small nerve fiber lesions have not been well explored yet.
• Researchers conducted a cross-sectional study to understand the association between vitamin D deficiency and DPN development in 230 older patients (mean age, 67 years) with T2D for about 15 years who were recruited from Beijing Hospital between 2020 and 2023.
• All patients were evaluated for DPN based on poor blood sugar control or symptoms such as pain and sensory abnormalities, of which 175 patients diagnosed with DPN were propensity-matched with 55 patients without DPN.
• Vitamin D deficiency, defined as serum 25-hydroxyvitamin D circulating levels below 20 ng/mL, was reported in 169 patients.
• Large nerve fiber lesions were evaluated using electromyography, and small nerve fiber lesions were assessed by measuring skin conductance.

TAKEAWAY:

• DPN was more prevalent in patients with vitamin D deficiency than in those without (80.4% vs 63.9%; P = .009).
• Vitamin D deficiency was more likely to affect large fiber lesions, suggested by longer median sensory nerve latency, minimum latency of the F-wave, and median nerve motor evoked potential latency than those in the vitamin D–sufficient group.
• Furthermore, vitamin D deficiency was linked to large fiber neuropathy with increased odds of prolongation of motor nerve latency (odds ratio, 1.362; P = .038).
• The electrochemical skin conductance, which indicates damage to small nerve fibers, was comparable between patients with and without vitamin D deficiency.

IN PRACTICE:

This study is too preliminary to have practice application.

SOURCE:

This study was led by Sijia Fei, Department of Endocrinology, Beijing Hospital, Beijing, People's Republic of China, and was published online in Diabetes Research and Clinical Practice.

LIMITATIONS:

Skin biopsy, the "gold-standard" for quantifying intraepidermal nerve fiber density, was not used to assess small nerve fiber lesions. Additionally, a causal link between vitamin D deficiency and diabetic nerve damage was not established owing to the cross-sectional nature of the study. Some patients with T2D may have been receiving insulin therapy, which may have affected vitamin D levels.

DISCLOSURES:

The study was supported by grants from the National Natural Science Foundation of China and China National Key R&D Program. The authors declared no conflicts of interest.