Symptom- and function-based neuropathy classifications and their relationships with quality of life in type 2 diabetes

Abstract Background Diabetic neuropathy is a major contributor to disability and reduced quality of life (QoL) in individuals with type 2 diabetes. Although both symptom-based and function-based neuropathy scales are widely used, their relative contributions to different QoL domains remain insufficiently understood. Objectives To examine the associations between symptom-based (Neuropathy Symptom Score, NSS) and function-based (Total Neuropathy Score, TNS) neuropathy classifications and multidimensional QoL using the 36-Item Short Form Health Survey (SF-36) among patients with type 2 diabetes. Methods A cross-sectional study was conducted among 69 outpatients with type 2 diabetes. Participants completed standardized neuropathy assessments (NSS and TNS) and the SF-36 QoL questionnaire. Descriptive analyses compared clinical and QoL characteristics across mild–moderate versus severe neuropathy categories for both NSS and TNS. Multivariable logistic regression using stepwise elimination based on the Akaike Information Criterion (AIC) identified predictors of poor QoL (defined as SF-36 domain scores <50). Principal component analysis (PCA) explored multivariate relationships among, patients’ characteristics neuropathy scores, metabolic factors, comorbidities, and QoL domains. Results Severe neuropathy was consistently associated with poorer physical function ( p < 0.001 and p = 0.015 for NSS and TNS-based classification, respectively). Significant associations were found for severe neuropathy against physical role limitation ( p = 0.009), pain ( p = 0.014), social function ( p = 0.031), and emotional role limitation ( p = 0.025). The association was not significant between severe neuropathy and general health in both NSS and TNS-based classifications with p -values 0.073 and 0.800, respectively. In regression models, male sex was associated with better physical function (OR 0.26, 95% CI 0.07–0.86), whereas older age (OR 1.13 per year, 95% CI 1.02–1.28) was linked to poorer physical role limitation. Insulin use independently predicted worse physical role functioning (OR 7.95, 95% CI 1.65–57.20). Higher NSS scores were consistently associated with poorer physical function (OR 1.61, 95% CI 1.12–2.43) and impaired vitality (OR 2.19, 95% CI 1.25–4.36). Conclusions Symptom-based and function-based neuropathy classifications are strongly associated with a single or multiple QoL domains in type 2 diabetes, with symptoms demonstrating greater predictive value than functional deficits. Neuropathy severity, metabolic factors, and comorbidities collectively shape QoL through both shared and independent pathways.