CARDIOVASCULAR RISK AND SLEEP APNEA SYNDROME
The sleep apnea syndrome (SAS) is a disorder characterized by intermittent narrowing (hypopnea) and/or total closure (apnea) of the upper airway during sleep.
The prevalence of SAS in the general population is approximately 20% being defined as an apnea hypopnea index (AHI) greater than five events per hour. It is 2 to 9% if defined as an AHI greater than five events per hour accompanied by daytime sleepiness. Therefore the importance of recognizing, diagnosing and treating this medical condition.
Several mechanisms are likely to be involved, including sympathetic overactivity, selective activation of inflammatory molecular pathways, endothelial dysfunction, coagulation abnormalities and metabolic dysregulation. The latter may involve insulin resistance and disorders of lipid metabolism. Sleep apnea thus activates the same pathways as does obesity, several epidemiological association studies supporting the fact that SAS is a risk factor for cardiovascular disease. Longitudinal cohort studies also provide evidence that patients with untreated severe sleep apnea have an increased rate of cardiovascular events.
Due to intermittent hypoxemia and sympathetic activation, the patients with severe OSAS are exposed to long term cardiovascular consequences (resistant arterial hypertension, stroke, myocardial infarction, cardiac arrhythmias).
The diagnostic approach includes: patient history (snoring, witnessed apneas, daytime somnolence), clinical examination (obesity, large neck size, arterial hypertension), screening (overnight continuous pulse- oximetry) and diagnostic confirmation by cardio- respiratory polygraphy and/or polysomnography (determination of Apnea Hypopnea Index.
In the context of the current epidemics of obesity, hypertension, atrial fibrillation, and heart failure, the prevalence and consequences of both SAS are likely to increase. Physicians need to consider how to treat such patients, given that CPAP treatment for obstructive sleep apnea is highly effective and essentially totally safe, and that the evidence is suggestive that sleep apnea is a risk factor for cardiovascular disease, all patients with severe sleep apnea should be treated to reduce cardiovascular risk.