Elevated glycosylated hemoglobin is associated with subclinical neuropathy in neurologically asymptomatic diabetic patients: a prospective study.

The association between poorly controlled diabetes and higher risk of polyneuropathy is well established. The American Diabetes Association recommends that glycosylated hemoglobin (HbA1c) should be less than 7%. Most previous studies, which reported HbA1c correlation with polyneuropathy, used higher HbA1c cut points and focused on neurologically symptomatic patients. This study evaluated the correlation of HbA1c levels, using the 7% cut point, with abnormal nerve conduction studies in diabetic patients in the subclinical stage of polyneuropathy. Fifty neurologically asymptomatic diabetic patients were included. HbA1c was measured at time of inclusion and 3 months later followed by nerve conduction studies. Univariate and multivariate analyses with logistic regression models were used to study the association of different patient characteristics with abnormal nerve conduction studies. Fifteen women and 35 men were studied. Half of patients had elevated HbA1c and half had HbA1c <7%. Twenty-six patients (52%) had subclinical neuropathy (18 men, 8 women). In multivariate analysis, HbA1c was the most important factor predicting higher risk of subclinical neuropathy [adjusted odds ratio 10.71 (2.49, 46.01), P < 0.005]. Therefore, nerve conduction studies abnormalities commonly exist in diabetic patients in the subclinical stages of polyneuropathy, and are highly correlated to HbA1c levels. Therapies for diabetic neuropathy should target the early stages of the disease.