OBJECTIVE -The aim of the current study was to determine the independent clinical risk factors for predicting morphological severity of distal diabetic sensorimotor polyneuropathy (DSP) as determined by fiber density (FD) on sural nerve biopsy. RESEARCH DESIGN AND METHODS -A total of 89 patients with both type 1 and type 2 diabetes, ascertained from a large therapeutic randomized clinical trial, were included in this observational cohort study. Morphological severity of DSP was expressed as the

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... myelinated FD in the sural nerve biopsy. General linear models were used to assess the relationship between the morphological severity of DSP and various clinical risk factors. RESULTS -Glycated hemoglobin (GHb) was significantly related to FD in univariate and multivariate regression analyses. This relationship was present in models in which GHb was handled either as a continuous variable or as a categorical variable with the highest significance level, with a GHb cutoff level of 9%. After dividing patients into groups with optimal to moderate (GHb Յ9%) and suboptimal (GHb Ͼ9%) glycemic control, the difference in FD between the two groups ranged between 3,461 and 2,334 per mm 2 . FD was also significantly related to duration of diabetes and age of the patient. CONCLUSIONS -The severity of peripheral DSP expressed by morphological criteria was significantly related to glycemic control in type 1 and type 2 diabetic patients. Inconsistent with previously published electrophysiological data demonstrating a correlation between height and conduction velocity, increasing height is not associated with morphological severity. Based on the results of the present study, it might be hypothesized that improving glycemic control will lessen severity of DSP in terms of FD loss in subjects with diabetes.