Original ArticleMarkers of glycemic control and insulin resistance in non-diabetic patients with Obstructive Sleep Apnea Hypopnea Syndrome: Does adherence to CPAP treatment improve glycemic control?
Introduction
Obstructive Sleep Apnea Hypopnea Syndrome (OSAHS) is a common disorder, affecting about 4% of middle-aged men and 2% of middle-aged women [1]. OSAHS is characterized by repetitive episodes of partial or complete obstruction of the upper airway during sleep, associated with increasing respiratory efforts, with a consequent oxyhemoglobin desaturation, sleep fragmentation and daytime symptoms (most commonly excessive sleepiness) [2]. Accumulating evidence suggests that intermittent hypoxia and oxyhemoglobin desaturation, both hallmarks of OSAHS, may independently affect energy metabolism, resulting in impaired glucose and lipid metabolism [3], as well as insulin resistance and metabolic syndrome [2], [3], [4]. Additionally, OSAHS has been proposed as an independent risk factor for type 2 diabetes [4]. The association between OSAHS and insulin resistance, independently of obesity, has been emphasized in the literature. Indeed, insulin resistance, as quantified by several techniques, mainly the homeostatic model assessment (HOMAIR) [5], has been attributed to visceral obesity, a common characteristic of OSAHS patients, as well as to the increase of sympathetic activity due to sleep fragmentation and intermittent hypoxia [6], [7].
Continuous Positive Airway Pressure (CPAP) is the primary treatment for OSAHS since it eliminates upper airway collapse during sleep and improves sleep fragmentation, daytime symptoms and quality of life [2]. Moreover, it has been demonstrated that CPAP improves several serum cardiovascular risk factors [8], [9] but its efficacy on insulin sensitivity is still not clarified [10], [11], [12] in OSAHS patients. In addition, it appears that the effect of CPAP on glycated hemoglobin (HbA1C) levels of non-diabetic OSAHS patients has not been adequately studied.
Therefore, the aim of the present study was to examine the effect of adherence to CPAP therapy on the modification of levels of markers of glucose dysmetabolism (fasting glucose levels and HbA1C) and insulin resistance (HOMAIR and fasting insulin levels) after 6 months of treatment.
Section snippets
Patients
Patients with newly polysomnographically confirmed OSAHS (Apnea Hypopnea Index [AHI] ⩾ 15/h) were initially recruited. All of them had presented to the Sleep Unit of “George Papanikolaou” General Hospital, Thessaloniki, Greece, reporting symptoms suggestive of sleep-related breathing disorders and had never been previously diagnosed or treated for OSAHS. The study was approved by the Ethics Committee and all participants gave their written informed consent, after being fully informed of the study
Results
Between January and December 2006, 276 patients were referred to the Sleep Unit reporting sleep-disordered breathing. Of those patients, 64 with OSAHS (i.e., AHI ⩾ 15 events per hour), who filled the inclusion criteria, consented to participate in the study. Eight patients of the 64 initially recruited, were withdrawn from the study due to significant reduction of their weight (ΔBMI, ⩾5%) (n = 3), surgery in the upper airway, (n = 2), or loss from follow-up (n = 3).
The remaining 56 patients (50 males,
Discussion
The present study evaluated the effect of adherence to CPAP treatment on glucose metabolism and insulin resistance in non-diabetic patients with OSAHS. Our main finding is that effective CPAP treatment for 6 months significantly improves HbA1C but not insulin resistance. Several studies have previously reported elevated levels of markers related to metabolic syndrome in OSAHS patients [16], [17], [18], [19]. Additionally, the effect of CPAP on insulin resistance has been the subject of several
Conflicts of interest
All authors have no conflicts to disclose.
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