[Autonomic neuropathy in type-2 diabetes, lessons from Okamoto Diabetes Study].

Clinically important diabetic autonomic neuropathy includes constipation, diarrhea, neurogenic bladder, impotence, dry skin, arterio-venous shunt in the lower extremities, reduced heart rate variability with tachycardia, orthostatic hypotension, and dysautoregulation of the cerebral blood flow. To investigate the prevalence, clinical characteristics and risk factor for diabetic complications, prospective epidemiological study (Okamoto Diabetes Study) has been started since 1991. Autonomic neuropathy was judged from the results of RR interval variation (CV < or = 1.5) and/or orthostatic change of systolic blood pressure (deltaSBP > or = 30 mmHg). The prevalence of autonomic neuropathy was 28% in type-2 diabetes enrolled in the Okamoto Diabetes Study. Aging, duration of diabetes, higher systolic blood pressure and HbA1c levels were independent risk factors for autonomic neuropathy. Frequent association with macrovascular complications in the subjects with autonomic neuropathy resulted in poor prognosis, especially due to cardiovascular events. The 55 subjects (19% of the 286 subjects already died) had died suddenly. Cause of sudden death in these subjects is still unclear, but silent myocardial infarction due to autonomic neuropathy may be, at least in part, one of the major causes of unexpected sudden death in type-2 diabetes.