Comparison of Diabetic Polyneuropathy and Cardiac Autonomic Neuropathy in Type 1 and Type 2 Diabetes Mellitus

Aim: To compare diabetic polyneuropathy (DPN) and cardiac autonomic neuropathy (CAN) between T1DM and T2DM patients. Methods: This study enrolled 66 T1DM and 79 T2DM patients. DPN was evaluated using three different methods: clinical examination, using neuropathy symptom score (NSS) and neuropathy disability score (NDS), current perception threshold (CPT) using Neurometer, and nerve conduction studies (NCSs). CAN was assessed by cardiovascular autonomic reflex tests (CARTs). Results: The prevalence of DPN did not differ between T1DM and T2DM (p > 0.05 for all), however, the proportion of DPN depended on the method used and was highest with CPT (53.0% vs. 46.8%), followed by NCSs (44.1% vs. 41.2%) and clinical examination (25.8% vs. 31.6%). T2DM vs. T1DM patients were more often diagnosed with painful DPN (51.9% vs. 27.3%, p = 0.004), reduced perception of vibration (72.2% vs. 48.5%, p = 0.006), and autonomic neuropathy (59.5% vs. 32.3%, p = 0.001), while NCSs revealed more prevalent motor nerve dysfunction in T1DM compared to T2DM (41.2% vs. 19.6%). Multivariate regression analysis showed increased DPN risk with age and CAN risk with worsening of eGFR in T1DM. No significant associations remained after multivariate adjustment for T2DM. Conclusions: The prevalence of DPN is highly varied and depends on the diagnostic method used. T2DM patients more often had symptoms and signs of diabetic neuropathy. However, stronger associations with risk factors were observed in T1DM.