Factors associated with autonomic nervous function in type 1 and type 2 diabetic subjects free of clinical manifestations of autonomic neuropathy

Abstract

Even though autonomic diabetic neuropathy is highly prevalent and a noted risk factor for cardiovascular morbidity and mortality, very little is known about factors associated with it. We carried out standard autonomic nervous system function tests by means of a computerized portable system on 55 diabetic patients (22 with type 1 diabetes, 33 with type 2 diabetes) who had no signs or symptoms of autonomic diabetic neuropathy and on 10 age- and sex-matched healthy control subjects. Test results of patients with type 1 diabetes did not differ significantly from those with type 2 diabetes. Of the clinical, metabolic, and anthropometric variables considered, only the duration of diabetes was inversely and independently correlated to deep breathing test scores (E:I ratio value of deep breathing 1.38-0.009. years of diabetes; R2 = 0.25). The duration of diabetes was inversely correlated to variations in orthostatic systolic blood pressure (r = -0.37, p < 0.01). The prevalence of diabetic retinopathy (score: 1 = no; 2 = yes) was significantly higher in the diabetic group with lower deep breathing values (1.8 +/- 0.3 vs 1.0 +/- 0.0; p < 0.01). The prevalence of ischemic electrocardiographic alterations (score: 1 = no; 2 = yes) was significantly higher in the diabetic group with a poorer orthostatic systolic blood pressure response (1.4 +/- 0.1 vs 1.2 +/- 0.1; p < 0.01). This study suggests that 1) autonomic neuropathy is correlated to disease duration; 2) type of diabetes, present level of metabolic compensation, and anthropometric characteristics do not seem correlated to this complication; 3) diabetic retinopathy and ischemic cardiopathy may be correlated to autonomic neuropathy.