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

<jats:title>Abstract</jats:title><jats:p><jats:bold>Aims </jats:bold> 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.</jats:p><jats:p><jats:bold>Methods </jats:bold> 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 <jats:italic>t</jats:italic>‐test and longitudinal data by means of <jats:sc>anova</jats:sc>.</jats:p><jats:p><jats:bold>Results </jats:bold> VPTs increased over time in neuropathy patients, with no change in control patients (<jats:italic>P <</jats:italic> 0.001). Glycaemic control was better over that period in control patients but the rate of improvement in HbA<jats:sub>1c</jats:sub> 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.</jats:p><jats:p><jats:bold>Conclusions </jats:bold> 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.</jats:p>