Sleep Apnea Syndrome: More Than Benign Snoring. Implications for the Cardiovascular System
Sleep disordered breathing is a rather common problem in the general population. Apnea during sleep can be divided into three types: central, obstructive and mixed. In central apneas there is lack of both airflow and respiratory efforts. It is recognized by its waxing-waning pattern of respiration called Cheyne- Stokes respiration. Central sleep apnea is most commonly seen in patients with heart failure and its prevalence among this group of patients is estimated to be as high as 30-40%. Obstructive sleep apnea occurs approximately in 5-15% of the general population. It usually affects middle-aged men with an increased body-mass index and a large neck circumference. It is characterized by repetitive complete or partial obstruction of the upper airway during sleep, which is followed by increasing and ineffective respiratory efforts.
Sleep fragmentation in patients with sleep apnea syndrome results in sleepiness, fatigue, morning headaches and depression. This daytime presentation together with loud snoring, choking and pauses of respiration during sleep should make primary care physicians suspicious of sleep disordered breathing. The best method used for the diagnosis of sleep apnea syndrome is overnight polysomnography.
The pathophysiologic mechanisms, which take place in sleep apnea, include sympathetic activation, hypercoagulability, inflammation and production of pro-inflammatory cytokines, endothelial dysfunction, oxidative stress and metabolic dysfunction. All these mechanisms are associated with the development and progression of cardiovascular disease. There is a strong linkage between sleep apnea and hypertension, systolic and diastolic dysfunction of the left ventricle, congestive heart failure, coronary artery disease, cardiac arrhythmias, stroke and pulmonary disease.
Given the increased morbidity and mortality of patients with sleep apnea, an effective treatment must be started as soon as possible after the diagnosis is made. Currently, nasal continuous positive airway pressure constitutes first line therapy. This therapy improves both quality of sleep and cardiovascular and general outcomes.
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