Sleep is an important component of every clinician's health assessment. Common sleep disorders (eg, obstructive sleep apnea, chronic insomnia) have deleterious effects on the cardiovascular system when left untreated. In this column, we discuss sleep/cardiovascular neurobiology and highlight the impact of nurse-led programs for improving patients' sleep and cardiovascular health.

To reduce cardiovascular disease risk, people generally require 6 or more hours of uninterrupted sleep,1 which is composed of 2 types: rapid eye movement (REM) sleep and non-REM sleep.2 Non-REM sleep can be further divided into 3 substages (N1, N2, and N3) that reflect the lightest (N1) to deepest (N3) sleep. Sleep types/stages are quantified when a patient undergoes polysomnography, which records electrical activity in the cortex, measures cardiorespiratory parameters (eg, heart rate, respiratory rate, oxygen saturation), and calculates diagnostic indices (eg, sleep apnea index). Sleep stages are defined by their distinctive electroencephalogram (EEG) patterns.2-4 Sleep normally begins with the N1 stage when cortical neurons begin producing a synchronous EEG rhythm. The transition from N1 to N2 sleep follows as the EEG rhythm shifts toward a lower-frequency pattern that is interspersed with 2 distinctive types of high-amplitude EEG waves (sleep spindles and K complexes). The deepest stage of sleep (N3) follows-slow (0.5-4 Hz), high-amplitude, synchronized EEG waves characterize N3 sleep (the slow neural oscillations are called delta waves; N3 sleep is also called "slow-wave sleep").2-5

Short bouts of REM sleep normally alternate with longer periods of non-REM sleep. The REM sleep EEG is distinctly different from the signals observed during non-REM sleep.3 Similar to the EEG during wakefulness, the EEG rhythm is fast and desynchronized during REM sleep-REM sleep is associated with vivid dreaming, rapid movements of the eyes, and muscle atonia.2 The role of REM sleep in cardiovascular homeostasis is incompletely understood, although anatomical brain research has revealed how REM-sleep regulatory centers in the brainstem (pontine tegmentum) send projections to medullary regions that control sympathetic output (rostral ventrolateral medulla), suggesting that REM sleep may be important in regulating the sympathetic innervation of the heart and blood vessels.3,6 Non-REM sleep also has important implications for cardiovascular health-sympathetic outflow declines during sustained periods of non-REM sleep. When asleep, a patient's blood pressure should drop significantly, a phenomenon called "blood pressure dipping." Nondipping (the failure to produce a reduction in blood pressure by ~10% during sleep) is associated with cardiovascular morbidity.3 Obstructive sleep apnea and insomnia are examples of prevalent sleep disorders with detrimental cardiovascular effects-these conditions can fragment/reduce sleep (particularly the N3 and REM sleep stages) and impair blood pressure dipping.3,7 Prevalence estimates for insomnia range from 5% to 50% in the general population, whereas obstructive sleep apnea afflicts 3% to 53% of adults, with higher rates associated with men, older age, and obesity.7-10

Nurse-led programs have been important for understanding, treating, and preventing sleep disorders and their cardiovascular consequences. For example, Siebmanns et al11 and Kapella et al12 treated insomnia by developing cognitive behavioral therapy programs for patients with cardiac and pulmonary disorders, respectively. Both programs significantly improved patient-reported and objective sleep quality indicators. Urcan and Kolcu13 developed an educational program for patients to improve their sleep after experiencing a stroke, and Zhu et al14 found that indicators of poor sleep quality (eg, number of awakenings) were significantly associated with poorer glycemic management in patients with type 2 diabetes. To understand adherence to sleep apnea therapies, Sawyer et al15,16 studied the factors affecting patients' use of positive airway pressure ventilation, finding that the facilitators, barriers, and perceptions varied across patients-this knowledge could be used to tailor nurses' future interventions toward sleep apnea management. In fact, nurse-led interventions have been successful in improving continuous positive airway pressure adherence. Nurses also examined sleep in hospital settings and provided recommendations to enhance patients' abilities to sleep in intensive care units, where lighting and noise can be particularly disruptive.17-21

In summary, healthy sleep is critical for cardiovascular health. Nurses have been designing, testing, and implementing novel approaches toward improving sleep. Nurses' research, practice, teaching, and policy initiatives about sleep are vital components of the national/global strategies for cardiovascular disease prevention.

REFERENCES