Predictors of vibration perception threshold in type 2 diabetic patients with proliferative retinopathy

Distal peripheral neuropathy (DPN) is a troublesome complication of diabetes mellitus (DM). The factors associated with the disease are still incompletely understood. The purpose of this study was to investigate factors associated with vibration perception threshold (VPT) as a marker of DPN in a type 2 diabetic population with advanced microvascular disease.

The study included 203 diabetic patients (117 male, 86 female) with proliferative diabetic retinopathy. Subjects were investigated by questionnaires, clinical examinations, blood and urine sampling, and review of medical records in the period from November 2008 through April 2009. Presence of DPN was defined as VPT ≥25 V.

The mean (±SD) age was 65.2 (±9.9) years and median (IQR) diabetes duration was 18 (10-25) years. Forty-six per cent of subjects were found to have DPN, defined as a VPT ≥25 V by neurothesiometer testing. Prevalence of DPN was found to be associated with age (p=0.038), male gender (p=0.046), low haemoglobin (p<0.001), high erythrocyte sedimentation rate (p=0.03), uric acid values (p=0.034), and peripheral vascular disease (PVD) (p=0.003) in univariate analysis. Multivariate logistic regression analysis revealed male gender (OR 5.52; p<0.001) and low haemoglobin values (B=-0.58; p<0.001) to be independent predictors of VPT ≥25 V in subjects with proliferative retinopathy, while linear regression analysis revealed male gender (p<0.001), haemoglobin (p=0.001), age (p=0.04), and PVD (p=0.001) to be significant predictors of VPT.

This study reports a novel independent association of DPN with low haemoglobin values. In the study population with type 2 DM and proliferative retinopathy, DPN was also independently associated with male gender, age, and PVD. Further studies are needed to confirm the association with low haemoglobin and identify the underlying mechanism.