Effects of CPAP on Cardiovascular Risk in Obstructive Sleep Apnea (OSA) and Metabolic Syndrome

Patients with obstructive sleep apnea (OSA) are at increased risk of atherosclerotic morbidity and mortality.OSA is associated with the development and/or worsening of arterial hypertension, a traditional risk factor of atherosclerosis.Moreover, OSA has been linked to novel factors related to atherogenesis - metabolic syndrome,systemic inflammation,6 and oxidative stress.

Numerous studies have selectively examined the effects of continuous positive airway pressure (CPAP) ventilation, the primary treatment for OSA, on the traditional and novel risk factors of atherosclerosis. A recent metaanalysis of 16 randomized trials indicated that CPAP decreases blood pressure in patients with OSA.9 Furthermore, reductions in serum total cholesterol, C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-6 and IL-8 were demonstrated after effective CPAP therapy.In addition, CPAP was shown to reduce systemic oxidative stress.Improvements in insulin sensitivity have been reported in some,but not in all studies. Importantly, substantial evidence links the effects of CPAP to compliance with this treatment.

Most observational studies examined the effects of CPAP across a broad-range of OSA severity, and have included patients with and without the metabolic syndrome. Up to now, no study analyzed the effects of CPAP on glucose and lipid metabolism, systemic inflammation, oxidative stress, and the global cardiovascular disease (CVD) risk within the same cohort of subjects with severe OSA and concurrent metabolic syndrome. Importantly, the metabolic syndrome exacerbates CVD risk over and above that attributable to OSA alone. Therefore, reduction of CVD risk in patients with OSA and concurrent metabolic syndrome is of paramount importance.

The primary purpose of the present study was to determine, in patients with severe OSA and metabolic syndrome compliant to CPAP, the effects of 8-weeks therapy on the glucose and lipid profile, systemic inflammation, oxidative stress, and on the global CVD risk. The secondary goal was to analyze factors related to compliance with CPAP.

Inclusion criteria

• severe OSA (more than 30 obstructive apneas or hypopneas per hour of sleep and excessive daytime sleepiness)
• metabolic syndrome

Exclusion criteria

• endocrine or metabolic disorders other than metabolic syndrome
• history of myocardial infarction, angina or stroke
• inflammatory or other chronic disease
• respiratory disorder other than OSA
• neurological lesions
• regular use of sedative medication or alcohol