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Disturbed sleep is common in heart patients following coronary angioplasty and is an independent risk factor for poor cardiac outcomes, researchers reported.

In a study of patients successfully treated with percutaneous coronary intervention (PCI), those who reported the most symptoms associated with poor sleep had a 67% incidence of having a heart attack, undergoing repeat vascularization, or dying within 4 years of the procedure, compared with 12% among patients who reported no sleep disturbance symptoms.

Multivariate analysis revealed that each additional symptom of disturbed sleep (on a 10-symptom scale) was associated with a hazard ratio for adverse cardiac events of 1.2 (P=0.001), and that this association was largely driven by the link between sleep problems and repeat revascularization (repeat PCI hazard ratio, 1.9, P=0.003, CABG hazard ratio 1.5, P=0.001), researcher Steven E. Miner, MD, of the University of Toronto, and colleagues, wrote online in the Canadian Journal of Cardiology.

"The absolute attributable risk is high," the researchers wrote. "Further studies are needed to determine which sleep disorders are most associated with increased risk for cardiovascular disease and if interventions aimed at improving sleep will improve cardiac outcomes after PCI."

Disturbed sleep is increasingly recognized as a risk factor for cardiovascular disease (CVD).

In a widely publicized Dutch population-based trial known as the , researchers found that people who slept 6 hours a night or less were 23% more likely to develop coronary heart disease than people who slept at least 7 hours. The study also found that poor-quality sleep was associated with a 63% increase in risk.

Although the epidemiologic data are strong, the mechanisms that link sleep disturbance and CVD are not well understood, and studies examining the impact of disturbed sleep interventions on patients at risk for cardiovascular events are needed, the researchers wrote.

"What we don't have is randomized trials to tell us what it is about disturbed sleep that influences cardiovascular outcomes, and most of the studies that have been done have been in low-risk populations," Miner told 木瓜直播.

The newly published, cross-sectional prospective cohort study involved outpatients successfully treated with PCI at Southlake Regional Health Centre in Ontario, Canada. The center is the sole provider of angiography, angioplasty, and bypass surgery in an area that includes approximately 1 million people.

The 388 patients included in the analysis were assessed for sleep problems soon after having PCI using a 10 item True/False questionnaire. Patients were also asked if they had ever been diagnosed with obstructive sleep apnea and if they had ever been treated with continuous positive airway pressure (CPAP).

Intermediate follow-up was conducted by telephone between 7 and 10 months after the PCI, and long-term follow-up was conducted 4 years after PCI by mail or telephone. Study endpoints included death, death from cardiac causes, myocardial infarction, and repeated revascularization (PCI or CABG).

On average, the patients reported 3.1 disordered sleep disturbance symptoms, with the most prevalent symptoms being snoring (59%), frequent nocturnal urination (50%), daytime somnolence (43%) and waking during the night and being unable to go back to sleep (43%).

A total of 62% of patients had at least three symptoms and 25% had at least five.

In all multivariate models examined, the effect of sleep symptoms remained consistent and statistically significant.

The analysis revealed that:

• Only sleep symptoms (hazard ratio 1.2, P=0.003), diabetes mellitus (HR 1.8, P=0.01), and number of diseased vessels (HR 1.4, P=0.03) remained significantly associated with the primary endpoints.
• Each additional sleep symptom was associated with an increased hazard of hospitalization (HR 1.2, P=0.009), repeated angiography (HR 1.36, P=0.01), repeated PCI (HR 1.2, P=0.02), CABG (HR 1.36, P=0.01), stroke (HR 1.5, P=0.05), and new diagnosis of heart failure (HR 1.5, P=0.01), independent of other factors associated with increased risk.
• Sleep disturbance questions most strongly correlated with risk for primary outcomes included "I sometimes wake up gasping for breath" (HR 3.01, P<0.001), "I feel sleepy during the day" (HR 1.90, P<0.004), and "I often wake during the night and have trouble falling back to sleep" (HR 1.54, P<0.05).
• In patients with a definitive diagnosis of obstructive sleep apnea (n=102), the 4-year event rate was 30%.

Although the analysis suggests an association between disturbed sleep and adverse cardiovascular outcomes, further study is needed to confirm a causal relationship, the researchers wrote.

"There are many reasons for disturbed sleep including apnea, depression, and even restless legs syndrome," Miner said. "Apnea populations tend to be very different from restless legs populations, but they both have an increased risk for these events."

He added that studies are needed to determine if interventions that improve sleep reduce cardiovascular risk, and he said clinicians should routinely ask heart patients about their sleep habits.

"Many sleep disturbances are easily corrected with lifestyle changes, and patients who have risk factors for sleep apnea may need a sleep study," Miner said.

From the American Heart Association:

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