Nancy S. Redeker, PHD, RN, professor and associate dean of research, umdnj-school of nursing

Sleep and functional performance in heart failure by Nancy S. Redeker

Disturbed sleep and sleep disordered breathing are common among the 5 million Americans who have heart failure, a devastating chronic illness that is associated with death, disability and poor quality of life. Disturbed sleep consistently ranks among the most frequently reported symptoms in these patients, and may occur in as many as 70%. Sleep disordered breathing, including Cheyne-Stokes breathing and/or obstructive sleep apnea, occurs in 30-60% of heart failure patients and is associated with repetitive apneic and hypopneic events, frequent nocturnal arousals from sleep and excessive daytime sleepiness. However, there is evidence that some heart failure patients may have disturbed sleep that is unrelated to sleep disordered breathing.

Heart failure patients live with impaired functional performance — the ability to accomplish normal activities during the course of daily life. Although reported prevalence rates vary based on measurement methods and stage of heart failure, as many as 50% also suffer from clinical depression and the majority of heart failure patients report fatigue. Studies conducted with cardiovascular populations and patients with sleep apnea, and our own preliminary data with heart failure and cardiac surgery, suggest that sleep disturbance is common and contributes to decrements in functional performance, as well as fatigue and excessive daytime sleepiness.

Sleep is a multidimensional biobehavioral phenomenon. The contributions of specific characteristics of sleep disturbance (e.g., sleep duration, depth, fragmentation) and sleep disordered breathing to functional performance in heart failure have not been previously examined. Heart failure patients who are fatigued, depressed or excessively sleepy as a consequence of disturbed sleep may be unable to accomplish normal activities of daily living. The purpose of this research is to examine the contributions of both sleep and sleep disordered breathing to functional performance and to evaluate the extent to which this relationship is mediated by depression, fatigue and excessive daytime sleepiness. Understanding the specific attributes of sleep and the nature of the relationships between these aspects and functional performance is particularly important because functional performance is linked with mortality. Interventions to improve sleep may improve functional performance, and may also contribute to reductions in mortality.

	Figure 1: Wrist actigraph

Funded by the National Institute of Nursing Research of the National Institutes of Health, this ongoing four-year multi-site observational study involves recruitment of 400 patients who have stable heart failure. The protocol includes completion of a polysomnographic study, including EEG, chin EMG, eye movement recordings, ECG, and measurement of respiratory effort, nasal airflow (pressure transducer and thermistor) and oxygen saturation, obtained in the home environment with a miniaturized sleep recorder. Obtaining these measures in the home, a more comfortable environment, is likely to provide a more accurate picture of the patients’ typical sleep pattern than is possible in a sleep laboratory setting. In addition to polysomnography, questionnaires and three-day behavioral sleep recordings obtained with wrist actigraphs are used. This battery of measures has been selected to permit evaluation of physiologic, behavioral and subjective attributes of sleep disturbance, each of which contributes information about important attributes of sleep.

Wrist actigraphs are computerized electronic accelerometer-based monitors that record activity/rest patterns. The activity/rest data are downloaded into a personal computer. Using commercially available software, inferences are made about the timing, duration, and extent of fragmentation of sleep throughout a 24-hour time period. The algorithm upon which this software is based has been validated against polysomnography, the gold standard of sleep measurement. Unlike polysomnography, actigraphy is non-intrusive and permits evaluation of sleep-wake over extended periods of time in natural environments. In my extensive work with this technology over the past 15 years, actigraphy has proved to be highly reliable and sensitive to clinically important changes in sleep patterns over time, as well as to clinically significant group differences.

Data obtained from the Minimitter Actigraph. The top panel indicates the raw activity data for one study participant for one day. The middle panel shows the 24-hour period from 12 noon to 12 noon. The area marked with the aqua lines indicates time in bed. The remainder of the screen indicates calculated sleep and activity values.

We anticipate that data from the current observational study will be used as the basis for a future clinical trial designed to evaluate interventions to promote sleep in heart failure patients. Although recognition is emerging among scientists and clinicians about the high prevalence of sleep disordered breathing among patients with heart failure, and growing use of nasal continuous positive airway pressure (NCPAP) to treat it, less attention has been paid to other sources of sleep disruption, such as insomnia, among patients with heart failure. Behavioral strategies to reduce nocturnal arousals, such as cognitive behavioral therapy, music or massage, as well as judicious use of hypnotic medications, may be effective treatments for disturbed sleep among heart failure patients. The data obtained from the current study will provide baseline information from which to develop and test these interventions.

Our preliminary work with heart failure patients demonstrated that fragmented sleep was associated with decrements in physical function and mental health, and documented the severity of specific attributes of disturbed sleep among heart failure patients during daily life. Heart failure patients demonstrated poorer self-reported sleep quality and more fragmented sleep, but no shorter sleep duration, than a comparison group of adults who did not have heart failure.

The current work with heart failure patients builds on a series of published studies in which we determined the nature of sleep disturbance over the course of recovery after coronary artery bypass surgery and the impact of sleep disturbance on physical function and emotional well-being — important quality of life concerns. Our finding that pre-operative sleep disturbance was an important predictor of post-operative sleep disturbance and physical function at four and eight weeks after surgery underscores the potential importance of pre-operative screening and intervention for sleep disorders among these patients. Our work also documented that post-operative sleep problems continued through the eighth post-operative week and thereby suggested the need for continued evaluation and management of sleep problems over the course of recovery.

I am also engaged in an ongoing collaborative series of studies to improve the sleep of adults during acute care hospitalization. The focus of this work is the development of sleep-promoting interventions for hospitalized patients.

Nancy S. Redeker, PhD, earned a BA in sociology from Rutgers University, BSN and MSN from Seton Hall University and a PhD in nursing from New York University. Dr. Redeker has completed NIH-funded training in sleep disorders. Her work has been funded by the National Institutes of Health, the American Nurses Foundation, American Heart Association, and the American Association of Critical Care Nurses. Until 2003, she was on the faculty of the College of Nursing at Rutgers. She is professor and associate dean for research at UMDNJ’s School of Nursing.§