Established diabetic neuropathy seems irreversible despite improvements in metabolic and vascular risk markers--a retrospective case-control study in a hospital patient cohort

Abstract

Aims: To gain insight into the natural history of diabetic peripheral neuropathy (DPN) and its risk factors by means of sequential quantitative testing in a hospital patient cohort.

Methods: A retrospective case-control study involving 300 diabetic patients (100 subjects with neuropathy and 200 control subjects) attending Poole Hospital diabetes clinic between 1995 and 2002. All subjects had a detailed annual clinic assessment including vibration perception threshold (VPT) and physical and metabolic assessments and were categorized according to neuropathy status. Established neuropathy was defined as a VPT > 25 V. Cross-sectional data were analysed by means of a t-test and longitudinal data by means of ANOVA.

Results: VPTs increased over time in neuropathy patients, with no change in control patients (P < 0.001). Glycaemic control was better over that period in control patients but the rate of improvement in HbA1c over time was similar in both groups. Triglyceride and high-density lipoprotein cholesterol levels improved in both groups, with significantly greater change in the control group.

Conclusions: Data on reversibility of neuropathy are scarce and our 8-year series shows a continual deterioration in VPT in patients with a threshold > 25 V despite modest improvements in glycaemic control and lipid parameters. This work also supports a vascular association with neuropathy and identifies neuropathic patients as a high-risk cardiovascular group in whom, despite little influence on neuropathy itself, the above metabolic factors should be actively addressed.