Does impaired glucose metabolism cause polyneuropathy? Review of previous studies and design of a prospective controlled population-based study

In spite of extensive studies it is unclear whether impaired fasting glucose (IFG) or impaired glucose tolerance (IGT), i.e., impaired glucose metabolism (IGM), causes diabetic sensorimotor polyneuropathy (DSPN) or chronic idiopathic axonal polyneuropathy (CIAP); the results and conclusions vary considerably in different studies. Some studies suggest that IGM is a common and important cause of CIAP, whereas others do not. On reviewing these data, we judge that a considerable degree of this disparity may relate to differences in selection of patients, choice of controls, assessment of chronic glycemic exposure and of diabetic complications, and statistical power. Here we review previous studies, list the reasons that the issue needs further study, and outline a study now in progress to address the question more definitively.