Mild obstructive sleep apnea does not modulate baroreflex sensitivity in adult patients

Peer reviewe

Total duration of apnea and hypopnea events and average desaturation show significant variation in patients with a similar apneahypopnea index

Obstructive sleep apnea (OSA) is commonly diagnosed based on the apnea-hypopnea index (AHI). Presently, novel indices were introduced for sleep apnea severity: total duration of sleep apnea and hypopnea events (TAHD%) and a combined index including duration and severity of the events (TAHD% × average desaturation). Two hundred and sixty-seven subjects were divided based on their AHI into four categories (normal, mild, moderate, severe OSA). In the most severe cases TAHD% exceeded 70% of the recorded time. This is important as excessive TAHD% may increase mortality and cerebro-vascular complications. Moreover, simultaneous increase in duration and frequency of apnea and hypopnea events leads to a paradoxical situation where AHI cannot increase along severity of the disease. Importantly, the combined index including duration and severity of the events showed significant variation between patients with similar apnea-hypopnea indices. To conclude, the present results suggest that the novel parameters could give supplementary information to AHI when diagnosing the severity of OSA

Weight loss alters severity of individual nocturnal respiratory events depending on sleeping position

Weight loss is an effective treatment for obstructive sleep apnea (OSA). The mechanisms of how weight loss affects nocturnal breathing are not fully understood. The severity of OSA is currently estimated by the number of respiratory events per hour of sleep (i.e. apnea-hypopnea-index, AHI). AHI neglects duration and morphology of individual respiratory events, which describe the severity of individual events. In the current paper, we investigate the novel Adjusted-AHI parameter (incorporating individual event severity) and AHI after weight loss in relation to sleeping position. It was hypothesised that there are positional differences in individual event severity changes during weight loss. Altogether, 32 successful (> 5% of weight) and 34 unsuccessful weight loss patients at baseline and after 1 year follow-up were analysed. The results revealed that individual respiratory event severity was reduced differently in supine and non-supine positions during weight loss. During weight loss, AHI was reduced by 54% (p = 0.004) and 74% (p < 0.001), while Adjusted-AHI was reduced by 14% (p = 0.454) and 48% (p = 0.003) in supine and non-supine positions, respectively. In conclusion, the severity of individual respiratory events decreased more in the non-supine position. The novel Adjusted-AHI parameter takes these changes into account and might therefore contribute additional information to the planning of treatment of OSA patients

Amount of weight loss or gain influences the severity of respiratory events in sleep apnea

Severity of obstructive sleep apnea (OSA) is estimated based on respiratory events per hour [i.e., apnea–hypopnea index (AHI)]. The aim of this study was to investigate effects of weight change on the severity of respiratory events. Respiratory event severity, including duration and morphology, was estimated by determining parameters quantifying obstruction and desaturation event lengths and areas, respectively. Respiratory events of 54 OSA patients treated with dietary intervention were evaluated at baseline and after 5-year follow-up in subgroups with different levels of weight change. AHI, oxygen desaturation index (ODI) and obstruction event severities decreased during weight loss. In lower level weight loss, the decrease was milder in obstruction severity than in AHI and ODI, indicating that the decrease in the number of events is more focused on less severe events. In weight gain groups, parameters incorporating obstruction event severity, AHI and ODI increased, although increase was greater in parameters incorporating obstruction event severity. The number and severity of respiratory events were modulated differently by the level of weight change. AHI misses this change in the severity of respiratory events. Therefore, parameters incorporating information on the respiratory event severities may bring additional information on the health effects obtained with dietary treatment of OSA

Novel parameters reflect changes in morphology of respiratory events during weight loss

Apnea-hypopnea-index (AHI), disregarding the respiratory event morphology, is currently used in estimation of severity of obstructive sleep apnea (OSA). The purpose of the current study was to evaluate the potential of novel parameters in estimation of changes in severity of OSA during weight loss. Polygraphic data of 67 patients, 37 in the control (no weight loss) and 30 in the weight loss (>5%) groups was evaluated at baseline and after two year follow-up. Changes in the values of novel parameters, incorporating detailed information of respiratory event characteristics, were evaluated and compared with changes in AHI. The median AHI in the weight loss group decreased significantly during the follow-up. The number of shorter respiratory events decreased in the weight loss group, while the longer ones remained, increasing the median durations of the respiratory events by 20-62%. For this reason the decrease of the values of the novel parameters were smaller compared to AHI in the weight loss group. This suggests that the severity of OSA might not fall as linearly during weight loss as AHI suggests. Moreover, the novel parameters containing more detailed information on the morphology characteristics may provide valuable supplementary information for the assessment of the severity of OSA

Mild obstructive sleep apnea does not modulate baroreflex sensitivity in adult patients

Henry Blomster,1 Tomi P Laitinen,2 Juha EK Hartikainen,3,6 Tiina M Laitinen,2 Esko Vanninen,2 Helena Gylling,4,8 Johanna Sahlman,1 Jouko Kokkarinen,5&nbsp;Jukka Randell,5 Juha Sepp&auml;,1 Henri Tuomilehto4,7 1Department of Otorhinolaryngology, Institute of Clinical Medicine, 2Department of Clinical Physiology and Nuclear Medicine, 3Department of Internal Medicine, 4Department of Clinical Nutrition, School of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, 5Department of Respiratory Medicine, 6Heart Center, Kuopio University Hospital, 7Oivauni Sleep Clinic, Kuopio, 8Department of Medicine, Division of Internal Medicine, University of Helsinki, Helsinki, Finland Background: Obstructive sleep apnea (OSA) is a chronic and progressive disease. OSA is associated with increased cardiovascular morbidity and mortality, the risk being more frequently encountered with severe degrees of OSA. Increased sympathetic activation and impaired cardiac autonomic control as reflected by depressed baroreceptor reflex sensitivity (BRS) are possible mechanisms involved in the cardiovascular complications of OSA. However, it is not known at what stage of OSA that changes in BRS appear. The aim of this study was to evaluate BRS in patients with mild OSA. Methods: The study population consisted of 81 overweight patients with mild OSA and 46 body weight-matched non-OSA subjects. BRS, apnea-hypopnea index, body mass index, and metabolic parameters were assessed. The phenylephrine test was used to measure BRS. Results: Patients in the OSA group were slightly but significantly older than the non-OSA population (50.3&plusmn;9.3 years vs 45.7&plusmn;11.1 years, P=0.02). Body mass index, percentage body fat, blood pressure, fasting glucose, insulin, and lipid levels did not differ between the OSA patients and non-OSA subjects. Absolute BRS values in patients with mild OSA and non-OSA subjects (9.97&plusmn;6.70 ms/mmHg vs 10.51&plusmn;7.16 ms/mmHg, P=0.67) and BRS values proportional to age-related and sex-related reference values (91.4%&plusmn;22.7% vs 92.2%&plusmn;21.8%, P=0.84) did not differ from each other. BRS &lt;50% of the sex-specific reference value was found in 6% of patients with mild OSA and in 2% of non-OSA subjects (P=0.29). Conclusion: Patients with mild OSA did not show evidence of disturbed BRS in comparison with weight-matched non-OSA controls. Keywords: obstructive sleep apnea, baroreceptor reflex sensitivit