Sleep disordered breathing, daytime symptoms, and functional performance in stable heart failure.

SLEEP DISORDERED BREATHING (SDB), INCLUDING OBSTRUCTIVE AND CENTRAL SLEEP APNEA, IS COMMON IN PEOPLE WITH CHRONIC HEART FAILURE (HF) and appears to be associated with objective and self-report measures of functional performance,1,2 excessive daytime sleepiness,2,3 self-reported poor sleep,4 and depressive symptoms.1 However, findings have been inconsistent,5–7 and previous studies have not addressed the clinical or demographic factors that may contribute to both SDB and its daytime consequences in HF patients. Understanding the extent to which SDB may be associated with daytime symptoms and functional performance may help to identify patients who are at high risk for these problems and may benefit most from improvements in daytime function through treatment. Depending on the population studied, obstructive apnea (OSA) and/or central sleep apnea (CSA) occur in 24% to 82% of HF patients.5–14 The relative odds of HF in the Sleep Heart Health Study (SHHS), a study of sleep in cardiovascular cohorts, was 2.38 for people in the highest vs. lowest quartile of the respiratory disturbance index.15 As many as 50% of patients with either systolic HF5,8,12,16 or HF with preserved systolic function17 have OSA. Between 15% and 62% of systolic HF patients5,8,9,12,18,19 and 20% of patients17 with preserved systolic function have CSA. Most previous studies have focused on patients with systolic dysfunction19–22 and included only men or very small proportions of women2,3,6,20,21; however, 40% to 71%23,24 of patients with HF have preserved systolic function and women represent approximately 50% of patients with HF over the lifespan. Although SDB was associated with lower actigraph-recorded daytime activity duration in male HF patients2 and oxygen uptake,1 but not the shuttle-walk test, in another study,1 SDB has not been consistently related to self-reported physical function in HF patients.15,6,25 A study of 700 HF patients12 revealed that HF patients with CSA had lower 6-minute walk test (6m WT) distances than patients with OSA or patients with no SDB. However, the potentially confounding effects of age, gender, and clinical characteristics on SDB and functional performance were not evaluated. SDB has been associated with objective,32 but not self-report measures of sleepiness2,5–7,26 and depressive symptoms among HF patients.1 There was a linear relationship between SDB and vitality in the SHHS27 that included a small proportion of HF patients; but, to our knowledge, the extent to which SDB explains fatigue, a common and disabling symptom in HF patients, has not been examined. The purposes of this study were to evaluate: (1) the characteristics of SDB in community-residing patients with stable HF; (2) the demographic and clinical correlates of SDB severity and predominant central vs. obstructive apnea; and (3) the extent to which SDB explained objective sleep characteristics, symptoms (fatigue, excessive daytime sleepiness, self-reported sleep quality, depression), and functional performance (self-report, 6m WT, daily mobility) in these patients.