Sleep apnea a stand-alone mortality risk
An independent link between sleep apnea and mortality has been discovered by a group of Australian researchers, suggesting the prevention and treatment of this condition should be a higher priority for government bodies working to improve community health.
The study conducted by the Woolcock Institute of Medical Research in Sydney found moderate to severe obstructive sleep apnea (OSA) was associated with 33% mortality over 14 years compared to 7.7% mortality in people with no sleep apnea.
This is the first report to demonstrate an independent association between all-cause mortality and obstructive sleep apnea in a population-based cohort. The community-based sample of 380 people comprised men and women from the Western Australian town of Busselton who underwent investigation with a home sleep apnea monitoring device in 1990.
The study results confirm the pattern seen in clinic or hospital-based studies where people more severely afflicted by the disease may have potentially biased results. Dr Nathaniel Marshall, from the Woolcock Institute said the findings of the study have important implications for the direction of health policy in Australia.
“We already know that approximately 25% of men and 9% of women in the middle-age bracket in Australia stop breathing during sleep at least five times per hour,” he said. “However because sleep apnea is strongly associated with obesity, and its related diseases, it has been difficult in the past to produce clear evidence that increased mortality is a result of OSA and not because of other established causes.
“That evidence is now available and shows that moderate to severe sleep apnea is associated with about five times the risk of dying after you control for other factors that are already known to cause premature death.”
Dr Marshall said the study results highlight a need to increase research funding to investigate whether treatment of sleep apnea can decrease heart attacks, strokes and premature deaths.
“There is a need for high quality clinical trials looking at treatments for sleep apnea that are large enough and long enough to find out whether we can prevent disease or reduce mortality risk.” Professor Ron Grunstein, Head of Sleep and Circadian Research, Woolcock Institute said, “Obstructive sleep apnea is a deadly disease and it is now time for public health and medical practitioners as well as the general public to take it seriously.
“The health profession needs to look closely at ways of detecting sleep apnea in children, adolescents and young adults to prevent sleep apnea in the over 40 yrs age group. “Sleep apnea prevention is different to obesity prevention as genetic factors related to facial shape and structure also play a role in pathogenesis,” he said.
Woolcock Institute of Medical Research
PO Box M77 Missenden Road NSW 2050, Australia
"Severe sleep apnea sufferers more likely to die
Risk is five times higher than normal, but treatment can cut the odds "
WASHINGTON —" Shakespeare once called sleep the "balm of hurt minds."
People with the severe form of a disorder that interferes with sleep are several times more likely to die from any cause than are folks without apnea, researchers report in the latest edition of the journal Sleep.
The findings in the 18-year study confirm smaller studies that have indicated an increased risk of death for people with sleep apnea, also known as sleep-disordered breathing.
"This is not a condition that kills you acutely. It is a condition that erodes your health over time," Dr. Michael J. Twery, director of the National Center on Sleep Disorders Research, said in a telephone interview.
People with such disorders "have been sleep deprived for perhaps very long periods of time, they are struggling to sleep. If this is happening night after night, week after week, on top of all our other schedules, this is a dangerous recipe," said Twery, whose center is part of the National Heart, Lung and Blood Institute.
The institute estimates that 12 million to 18 million people in the U.S. have moderate to severe apnea. The condition is not always detected because the sufferer is asleep when the problem occurs and it cannot be diagnosed during a routine office visit with a doctor. Researchers tested the patients for sleep-disordered breathing in the laboratory and then followed them over several years.
Disrupted breathing depletes oxygen
For people with apnea, their upper airway becomes narrowed or blocked periodically during sleep. That keeps air from reaching the lungs. In some cases, breathing stops for seconds to a minute or so; the pauses in breathing disrupt sleep and prevent adequate amounts of oxygen from entering the bloodstream.
"When you stop breathing in your sleep you don't know it, it doesn't typically wake you up," Twery said. Instead, it can move a person from deep sleep to light sleep, when breathing resumes. But their overall sleep pattern is disturbed, and it can happen hundreds of times a night.
He said that a person typically will have four or five cycles per night of light sleep, deep sleep and REM (rapid eye movement) sleep, when most dreams occur. More deep sleep comes early in the night with more REM sleep closer to waking up. This pattern helps control hormones, metabolism and levels of stress.
The institute, part of the National Institutes of Health, says apnea has been linked to a greater risk of heart disease, high blood pressure, stroke, diabetes and excessive daytime sleepiness.
In the new report, the Wisconsin Sleep Cohort followed 1,522 men and women, ages 30 to 60. The annual death rate was 2.85 per 1,000 people per year for people without sleep apnea.
People with mild and moderate apnea had death rates of 5.54 and 5.42 per 1,000, respectively, and people with severe apnea had a rate of 14.6 per 1,000, researchers said.
Cardiovascular mortality accounted for 26 percent of all deaths among people without apnea and 42 percent of the deaths among people with severe apnea, according to the researchers led by Terry Young of the University of Wisconsin, Madison.
In the same issue of the journal Sleep, a separate study of 380 adults between 40 and 65 in Australia came to a similar conclusion. This study found that after 14 years, about 33 percent of participants with moderate to severe sleep apnea had died, compared with 6.5 percent of people with mild apnea and 7.7 percent of people without apnea.
No question, sleep apnea can be fatal
"Our findings, along with those from the Wisconsin Cohort, remove any reasonable doubt that sleep apnea is a fatal disease," said lead author Dr. Nathaniel Marshall of the Woolcock Institute of Medical Research in Sydney, Australia.
Apnea often is treated with a device that delivers continuous positive airway pressure through a mask over the nose and/or mouth. The U.S. study found that patients using the CPAP device had reduced death rates.
There has been debate over whether to use airway pressure to treat patients who are not sleepy in the daytime, the report noted.
The U.S. researchers noted that while theirs was a large study, 95 percent of the participants were white and most had adequate income and access to health care.
"It is likely that our findings may underestimate the mortality risk of SDB in other ethnic groups or the lowest socio-economic strata where there is poor awareness and access to health care," they said.
The U.S. research was supported by the National Institutes of Health. The Australian study was supported by the Australian National Health and Medical Research Council.