Prognostic Impact of Sleep Duration and Sleep Efficiency on Mortality in Patients With Chronic Heart Failure
Is subjective sleep duration paralleled by abnormal sleep efficiency in heart failure, and is objective sleep efficiency an independent risk factor for death in this population?
Congestive heart failure (CHF) patients (n = 411) referred for polysomnography (PSG) between 2002 and 2009 were studied. Subjects with stable ischemic and nonischemic cardiomyopathy were included, regardless of sleep disordered breathing symptoms. HF due to valvular causes was excluded. Subjects with known positive airway pressure treatment or chronic oxygen use were also excluded. Self-reported sleep duration (SDSR) and sleep efficiency (SEPSG) were assessed by standardized questionnaire and PSG. The primary outcome was all-cause mortality, and was determined by medical documentation.
Two hundred subjects did not meet inclusion criteria, and 23 were lost to follow-up. Thus, 188 patients with CHF were analyzed after a mean follow-up period of 44 ± 26 months. Fifty-seven (30%) CHF patients died during follow-up, representing a mortality rate of 8.4 per 100 individual-years. SEPSG in CHF patients from the highest quintile of SDSR (≥9 hours) was significantly lower compared with the middle quintile (7.25-8 hours; 71 ± 15% vs. 77% ± 11%; p = 0.032) and similar to the lowest quintile (≤5.75 hours; 71 ± 15% vs. 71 ± 16%; p = 0.950). SEPSG independently predicted death in a multivariable model after accounting for age, left ventricular ejection fraction, cause of CHF, and class of CHF (hazard ratio per 5% increase, 0.85; 95% confidence interval, 0.77-0.93; p < 0.001).
The authors concluded that subjective long sleepers with CHF have poor sleep efficiency, and that objectively measured SEPSG strongly predicts mortality in CHF patients.
Even though laboratory measurement of sleep may not reflect home sleep habits, this present study compliments prior studies demonstrating that subjective long sleepers have poor sleep quality. These CHF patients who reported to be long sleepers were found to have impaired sleep efficiency and predicted mortality independent of age, gender, cause, and severity of CHF or sleep disordered breathing. Of note, rates of cardiovascular risk factors and medication usage were similar among groups. It is unclear whether this conclusion can be extrapolated to a population with healthy heart function, but certainly highlights the importance of assessment of sleep characteristics of CHF patients with an objective PSG. To show a clinical benefit from improvement in sleep efficiency in this population will require further investigational studies.
Keywords: Sleep Initiation and Maintenance Disorders, Follow-Up Studies, Chronic Disease, Ventricular Function, Left, Lost to Follow-Up, Risk Factors, Sleep Apnea Syndromes, Prognosis, Incidence, Polysomnography, Cardiomyopathies, Heart Failure, Stroke Volume, Oxygen
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