J-Shaped Relationship Between Visceral Fat Area and Large-Nerve Fiber Dysfunction Estimated by Vibration Perception Threshold in Type 2 Diabetes: A Cross-Sectional Study.

Introduction: Although obesity has been implicated in the development of diabetic peripheral neuropathy (DPN), the relationship remains controversial. This study aimed to clarify the association between visceral fat area (VFA) and large nerve fiber dysfunction, as estimated by vibration perception threshold (VPT), in young and middle-aged Chinese patients with type 2 diabetes mellitus (T2DM).

Methods: This cross-sectional study enrolled 501 adults aged 18-65 years with T2DM between March 2020 and August 2024. Visceral fat area was assessed using bioelectrical impedance analysis, and large nerve fiber dysfunction was evaluated via vibration perception threshold measurement. Multivariable logistic regression, generalized additive models, smooth curve fitting, and two-piecewise regression analyses were employed to explore the relationship between VFA and VPT.

Results: Among the participants, 27.5% exhibited abnormal VPT. After adjustment for potential confounders, a nonlinear J-shaped association between VFA and VPT was observed. Two-piecewise logistic regression revealed a turning point at 133.9 cm² with a significant threshold effect (P for log-likelihood ratio test = 0.020). Below this threshold, VFA showed no significant association with abnormal VPT (OR = 1.00; 95% CI, 0.90-1.11; P = 0.978). However, above this threshold, each 10 cm² increase in VFA was associated with a 22% higher risk of abnormal VPT (OR = 1.22; 95% CI, 1.07-1.40; P = 0.003). Subgroup analyses and interaction tests were not significant (all P > 0.05).

Conclusion: In young and middle-aged patients with T2DM, the relationship between visceral fat accumulation and large nerve fiber dysfunction exhibits a J-shaped curve. Notably, VFA exceeding the defined threshold of 133.9 cm² significantly increased the risk of impaired nerve function as measured by VPT.