Epidemiology of polyneuropathy in diabetes and prediabetes.

Diabetic distal symmetric sensorimotor polyneuropathy (DSPN) represents a major health problem, associated with excruciating neuropathic pain, increased morbidity and impaired quality of life. The understanding of its epidemiology is difficult due to methodological issues. Inconsistency in the selection of diagnostic procedures renders comparison between studies problematic. Further problems arise from selection bias due to the inclusion of hospital-based populations. DSPN affects approximately 30% of hospital-based populations, 20% of community-based samples, and 10% of the diabetic population identified by screening. Chronic painful DSPN is present in 13-26% of diabetic patients. Between 25% and 62% of patients with idiopathic peripheral neuropathy have prediabetes. Among pre-diabetic subjects, 11-25% exhibit peripheral neuropathy and 13-26% neuropathic pain. Evidence from population-based studies indicates that there is a gradient in the prevalence of neuropathy. Indeed, the highest frequency is found in patients with manifest diabetes mellitus, followed by individuals with impaired glucose tolerance, then impaired fasting glucose and, finally, those with normoglycemia. The most important etiologic factors are poor glycemic control, age, diabetes duration, visceral obesity, height, hypertension, age, smoking, hypoinsulinemia, and dyslipidemia. Clinic-based data suggest that DSPN is associated with increased mortality in diabetes, but confirmatory prospective population-based studies are required.