The Impact of Diabetes and Metabolic Syndrome Burden on Pain, Neuropathy Severity and Fiber Type.

Objective: Determine the association between diabetes and metabolic syndrome (MetS) burden (number of MetS criteria fulfilled) and pain, neuropathy severity, and fiber type involvement in individuals with established polyneuropathy.

Methods: The Peripheral Neuropathy Research Registry was queried for individuals with type 1 and type 2 diabetes (DPN) and non-diabetic peripheral neuropathy (cryptogenic sensory polyneuropathy and prediabetes) using cross-sectional observational data. Associations between diabetes or MetS burden and pain presence (yes/no), neuropathy severity (Total Neuropathy Score reduced), and fiber type involvement (pinprick, vibration, and proprioception examination-small, large, mixed) using logistic, linear, and multinomial regression models were determined.

Results: A total of 1112 participants were included (265 DPN, 847 non-diabetic peripheral neuropathy [NDPN]). Compared to NDPN, DPN participants were more likely to have pain, higher neuropathy severity, and mixed fiber involvement. In adjusted models, diabetes was associated with pain (odds ratio [OR] 1.85, CI: 1.15-3.03) and severity (point estimate [PE] 0.84, CI: 0.27-1.42), but not fiber type involvement. As the MetS burden increased, pain, neuropathy severity, and mixed fiber type involvement increased (p < 0.05 for trend). In adjusted models, MetS burden was associated with pain (OR 1.23, CI: 1.06-1.41) but not severity or fiber type involvement.

Interpretation: Participants with DPN were more likely to have pain, greater neuropathy severity, and possibly more mixed fiber involvement than those with NDPN. Similarly, increasing MetS burden also led to more painful neuropathy and possibly more severe neuropathy with more mixed fiber involvement.