Variability of fasting plasma glucose and the risk of painful diabetic peripheral neuropathy in patients with type 2 diabetes

Aim The relationship between glycaemic variability and painful diabetic peripheral neuropathy (PDPN) in patients with type 2 diabetes (T2D) is unclear. The aim of this study was to investigate whether variations in fasting plasma glucose (FPG), as represented by the coefficient of variation (CV), were associated with the risk of PDPN in patients with T2D. Methods This case-control, retrospective study was conducted at a tertiary care hospital in Taiwan. We enrolled adults with T2D from January 1 through October 31, 2013. PDPN was diagnosed using the Michigan Neuropathy Screening Instrument (MNSI) and Douleur Neuropathique 4 (DN4) questionnaire. Variability in FPG was defined as a CV of visit-to-visit FPG for every 3-month interval during follow-up period before enrolment. Results A total of 2,773 patients were enrolled. One hundred patients with PDPN were randomly selected and paired with 175 consecutive patients with non-painful diabetic peripheral neuropathy and 351 patients with T2D without diabetic peripheral neuropathy, matched for age, gender, and diabetic duration. After multivariate adjustment, the FPG-CV was significantly associated with a risk of PDPN with a corresponding odds ratio of 4.08 (95% confidence interval [CI] of 1.60-10.42) and 5.49 (95% CI of 2.14-14.06) for FPG-CV in the third and fourth versus first FPG-CV quartiles, respectively, after considering glycated haemoglobin (HbA1c). Conclusion Long-term variability as evaluated by FPG-CV was associated to the risk of PDPN in adults with T2D. However, further studies are needed to know whether the FPG-CV is not simply a marker of the ambient hyperglycaemia.