Decreases in AHI at 3 months (non-significant) and at 6 months (with a tendency towards significance) after RDN were noted (median 16.3 events/h before RDN versus median 4.5 events/h after 6 months; p = 0.059). Also decreases in oxygen desaturation indices (ODI) at 6 months (median 13.0 events/h before RDN versus median 8.7 events/h; p = 0.11) and decreases in median Epworth Sleepiness Scale score at 6 months (9.00 points versus 7.00 points; p < 0.05) were also reported. In summary, in eight of ten patients an improvement in AHI was observed at 6 month (Fig. 24.2). There were two patients with mixed sleep apnea. In one of them, a reduction in sleep apnea indices was also observed with a change in AHI −30.5 events per hour at 6 months. In patients with improvement in AHI, a significant decrease in 24-h, daytime, and nighttime ambulatory Blood pressure monitoring (ABPM) levels was observed, the latter being most pronounced (median: −8/−4 mmHg, −12/−5 mmHg and −10/−8 mmHg for 24-h, daytime, and nighttime, respectively; p < 0.05 for all).

Along with blood pressure reduction and sleep apnea course improvement significant decreases in plasma glucose concentration 2 h after glucose administration at 3 and at 6 months (median 7.0 mmol/dL versus median 6.4 mmol/dL at 6 months; p < 0.05) and in hemoglobin A1C level at 6 months (median 6.1 % versus median 5.6 %; p < 0.05) were demonstrated.

This study confirmed that RDN lowers blood pressure in patients with resistant hypertension [39, 40] and endorsed the work of Mahfoud et al. documenting that RDN in humans improves indices of insulin action and glucose metabolism [41]. However, this publication extended previous work by documenting that the blood pressure and metabolic benefits of renal denervation include patients with sleep apnea and improve the course of the disease. Because these data were observational, the study could not identify the exact mechanism responsible for any amelioration of sleep apnea. Nonetheless, it should be emphasized that RDN influences key mechanisms regulating sympathetic activation. The efferent sympathetic renal nerves can affect control of renal vascular resistance, increase renin release, and regulate sodium and water excretion [12]. The afferent renal nerves enhance the activity of the sympathetic nervous system. It has been also suggested that, in conditions of high-sodium dietary intake, activation of the afferent renal nerves contributes to the arterial baroreceptor-mediated suppression of efferent sympathetic renal nerves in the overall goal of preventing sodium retention and maintaining water and sodium homeostasis [12, 42]. Therefore, RDN in patients with resistant hypertension and OSA might attenuate the effects of sympathoactivation additionally and independently of CPAP treatment. Lastly, it need to be considered that the fall in blood pressure may itself contribute to the attenuation of sleep apnea.