Sleep apnea Rx may not eliminate heart risk
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Treatment of long-standing or severe sleep-disordered breathing, also known as sleep apnea, cannot always eliminate the risk of cardiovascular disease, stroke and death, according to two studies in The New England Journal of Medicine this week.
People with sleep apnea involuntarily stop breathing dozens of times each night, causing them to gasp for breath. Obstructive sleep apnea (OSA) occurs when the airway becomes blocked by tissue such as the tonsils or base of the tongue, whereas central sleep apnea occurs when the respiratory system stops working in the absence of a blockage.
A new study by Dr. Vahid Mohsenin and colleagues at Yale University School of Medicine in New Haven, Connecticut, supports prior research findings, that OSA raises the risk of stroke or death.
“Previous studies were primarily cross-sectional,” Mohsenin explained, “and could not answer the question whether OSA caused stroke, or whether stroke was associated with sleep apnea due to neurological deficit.”
“Our study was prospective in patients without prior stroke followed over time,” he said. “We basically showed a temporal relationship between sleep apnea and stroke.”
Among 1022 patients ages 50 or older who were evaluated for sleep apnea, between 1997 and 2000, 697 were diagnosed with OSA and most received treatment including weight loss, upper airway surgery and CPAP—continuous positive airway pressure in which a facemask is used to introduce a gentle stream of air to keep the airways open during the night.
During follow up lasting a median of 3.4 years, there were 22 strokes and 50 deaths in the OSA group compared with just 2 strokes and 14 deaths in the comparison group.
Mohsenin pointed out that OSA treatments were not without benefit, and that the rate of events would have been higher in their absence.
“You have to remember that these individuals were exposed to sleep apnea for years before they were diagnosed and treated, so most likely they had damage to the vasculature prior to their diagnosis,” he explained.
The key, he added, is to recognize patients with OSA early and institute treatment and lifestyle changes that will reduce risk.
In the second study, Dr. T. Douglas Bradley, from the University of Toronto, and colleagues enrolled patients with severe central sleep apnea and failing hearts to CPAP or no CPAP.
In addition to reducing the frequency of episodes of sleep-disordered breathing by about 50 percent, CPAP also increased nighttime oxygen uptake and improved heart function. These benefits were sustained for up to 2 years.
Nevertheless, the overall rate of death and heart transplantation was similar in both groups. CPAP also failed to reduce hospitalizations or improve quality of life.
Although their trial lacks “the power to conclude with certainty that CPAP is ineffective in this patient population,” Bradley and his team maintain, “our data do not support its routine use to extend life in patients with central sleep apnea and heart failure.”
SOURCE: New England Journal of Medicine, November 10, 2005.
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