Detection of Subclinical Diabetic Neuropathy in Type 2 Diabetes: A Study of Nerve Conduction Parameters and Their Associations With Metabolic and Demographic Factors

Background Diabetic peripheral neuropathy (DPN) is one of the most common and disabling complications of type 2 diabetes mellitus (T2DM), affecting a substantial proportion of patients and contributing to significant morbidity and reduced quality of life. Importantly, up to one-third of individuals may already have subclinical electrophysiological abnormalities at the time of diagnosis, highlighting the need for early detection before symptoms become clinically evident. A considerable proportion of patients develop nerve conduction abnormalities even before neuropathic symptoms appear on clinical examination. Nerve conduction studies (NCS), including F-wave assessment, offer a sensitive approach to detecting early, subclinical nerve dysfunction. This study evaluated detailed NCS parameters in neurologically asymptomatic T2DM patients and examined their associations with key metabolic and demographic factors. Methods A prospective, cross-sectional, observational study was conducted involving 60 participants aged 18-70 years, comprising 30 neurologically asymptomatic individuals with T2DM and 30 age- and sex-matched healthy controls. Neurologically asymptomatic status was confirmed through a structured clinical neurological examination and screening using the Michigan Neuropathy Screening Instrument (MNSI), with participants excluded if they demonstrated clinical signs or scored above the diagnostic threshold for neuropathy. Standardized exclusion criteria were applied to minimize confounding, including known vitamin B12 deficiency, chronic alcohol use, renal insufficiency, thyroid dysfunction, exposure to neurotoxic medications, or other neurological disorders. Motor and sensory NCS were performed on upper- and lower-limb nerves to assess distal latencies, conduction velocities, compound muscle action potential (CMAP) amplitudes, sensory nerve action potential (SNAP) amplitudes, and F-wave minimum latencies. A sample size of 60 was determined based on feasibility and prior reports, acknowledging that no formal power calculation was performed and recognizing this as a limitation. Statistical analysis included independent Student's t-tests for between-group comparisons, and Pearson's correlation to explore associations with glycated hemoglobin (HbA1c), age, duration of diabetes, and body mass index (BMI), following verification of approximate normal distribution of continuous variables. Results Compared with healthy controls, participants with T2DM demonstrated significant impairments across the majority of NCS parameters (predominantly p < 0.001), characterized by prolonged distal and F-wave latencies, reduced CMAP and SNAP amplitudes, and slower conduction velocities in both upper- and lower-limb nerves. Correlation analysis showed weak-to-moderate associations between HbA1c, age, and duration of diabetes with key conduction indices (r values generally ranging from ±0.30 to ±0.75, p < 0.05), while BMI showed no meaningful correlation with NCS measures. Conclusion Neurologically asymptomatic T2DM patients showed early electrophysiological changes suggestive of subclinical DPN. NCS, including F-wave assessment, may aid early identification, though our cross-sectional design and small sample size limit causal conclusions regarding prevention or long-term outcomes.