Obstructive sleep apnea syndrome: the effect of diabetes and autonomic neuropathy

Several studies indicate an association between obstructive sleep apnea syndrome (OSAS) and diabetic autonomic neuropathy (DAN). Observed frequency of OSAS in diabetic patients with DAN varies between 26% and 30%. Excessive daytime sleepiness is one of the major clinical symptoms of sleep disordered breathing. Diabetics with autonomic neuropathy might have abnormal control of respiration during sleep, probably resulting in a reduced daytime sleepiness. We investigated the impact of autonomic diabetic neuropathy on clinical symptoms (e.g., daytime sleepiness, measured by Epworth Sleepiness Scale, ESS) in patients with suspected OSAS. We examined 196 patients suspected of sleep apnea (52 female, 144 male, mean age 58.7 yrs, mean BMI 30.57 kg/m2). All patients underwent overnight polysomnography and were tested for autonomic neuropathy by a method of measuring heart rate variabilty and heart rate response to the Valsalva maneuver, standing and deep breathing using a computerized data analysis system. Eighty diabetic subjects: 52 DAN-, 28 DAN+; 116 subjects without diabetes: 101 without autonomic neuropathy (AN), 15 AN+. The group of diabetics with DAN+ had a mean apnoea/hypopnea index (AHI) of 38.6/h, mean oxygen desaturation: 77.5%, mean ESS-Score: 9.86. Diabetic patients DAN-: mean AHI:30.4/h, mean oxygen desaturation: 79.3%, mean ESS-Score 9.73. Defining OSAS as AHI>5/h and ESS-Score>9, 46% of the diabetic patients DAN+ were positive, whereas in the DAN- group 61% met the criteria (non-diabetic patients without AN 50.5%; with AN: 60%). Although the group of diabetic patients with autonomic neuropathy had the lowest percentage of OSAS, statistical analysis showed no significance in comparisons between DAN-/DAN+ or diabetic/non-diabetic. In conclusion, although this study did not give statistical evidence, there is reason to assume that patients with diabetic autonomic neuropathy show fewer clinical symptoms of OSAS than those without it. The examination for OSAS might be indicated even without excessive daytime sleepiness because of elevated cardiovascular risk.