Sleep and Heart Disease
Sleep disordered breathing is common in patients with cardiovascular disease. Obstructive sleep apnea (OSA) has been associated with various cardiac conditions such as hypertension, heart failure, stroke, and arrhythmias. There is good evidence to suggest obstructive sleep apnea contributes to development of hypertension, and that therapy with positive airway pressure (PAP) improves blood pressure. Similarly, OSA has been implicated in incident strokes, and is also very common post-stroke. Sleep apnea in the form of obstructive or central sleep apnea, affects more than half of all heart failure patients. Obstructive sleep apnea may exacerbate heart failure by causing large negative intrathoracic pressure swings, nocturnal hypoxemia and hypercapnia, sympathetic overdrive, resulting in hypertension, endothelial damage and resultant premature atherosclerosis. Reversal of obstructive sleep apnea improves blood pressure, systolic contraction and autonomic dysfunction. Central sleep apnea with Cheyne-Stokes pattern (CSA-CSR) of respiration is a result of moderately to severely impaired cardiac function and is possibly indicative of high mortality. Treatment of CSA-CSR includes treating the underlying cardiac condition with medications, pacemakers, transplantation or positive airway pressure (PAP). In such patients PAP exerts unique effects to assist cardiac function and reduce pulmonary edema. Finally, in patients with atrial fibrillation, treating sleep apnea is associated with a 40% chance of recurrent atrial fibrillation in contrast to those left untreated, in whom the chance of a recurrence of atrial fibrillation goes up to 80%.
Sleep duration has also been linked to cardiovascular outcomes. A 2011 European Heart Journal review of 15 medical studies involving almost 475,000 people found that short sleepers had a 48% increased risk of developing or dying from coronary heart disease (CHD) in a seven to 25-year follow-up period (depending on the study) and a 15% greater risk of developing or dying from stroke during this same time. Interestingly, long sleepers averaging more than nine hours of sleep nightly also showed a 38% increased risk of developing or dying from CHD and a 65% increased risk of stroke. Some studies have also associated shorter sleep to worsening hypertension. Researchers caution that the mechanisms behind shortened and prolonged sleep and heart disease aren't completely understood, and that lack of sleep does not necessarily cause heart disease. More likely, sleep deprivation is associated with a lifestyle that increases risk factors for cardiovascular disease. People who are sleep-deprived show less variability in their heart rate, meaning that instead of fluctuating normally, the heart rate usually remains elevated, likely representing heightened stress hormones. Lack of sleep can also increase insulin resistance, a risk factor for type 2 diabetes mellitus. Sleep deprivation may also increase C-reactive protein, a marker of stress and inflammation and a risk factor for cardiovascular and heart disease. Irregular and shortened sleep hours also negatively impact appetite and metabolism, and promote weight gain.