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A new U.K. study was unable to reproduce recent findings that suggested chronic fatigue syndrome may be linked to a virus. But U.S. researchers emphasized that there are key differences between the studies.
The Sleep Education Blog reported on the previous research in October. The U.S. study identified DNA from the “XMRV” virus in the blood of 68 out of 101 people with CFS.
The new study was conducted in the U.K. DNA was extracted from blood samples of 186 people with CFS. They were screened for the XMRV virus and for another closely related virus.
Results published on Wednesday show that neither virus was detected in any of the samples. The authors suggested that the results may be a result of population differences between North America and Europe.
“We used very sensitive testing methods to look for the virus,” study co-author Myra McClure said in a news release. “If it had been there, we would have found it. We are confident that our results show there is no link between XMRV and chronic fatigue syndrome, at least in the U.K.”
But the institute behind the U.S. research questioned the methods of the U.K. study.
“This study did not duplicate the rigorous scientific techniques (used by the U.S. research team),” said a group statement. “Therefore it cannot be considered a replication study… Significant and critical questions remain as to the status of patient samples used in the U.K. study.”
Simon Wessely, another co-author of the U.K. study, also cautioned that their results are not conclusive. He said more research is needed to determine the fundamental cause of CFS.
"It is important to emphasize that today's findings do not invalidate all previous research,” said Wessely. “As ever in science, no single study is conclusive.”
CFS occurs four times more often in women than in men. The CDC notes that CFS is neither a form of depression nor a mental illness.
“There is now abundant scientific evidence that CFS is a real physiological illness,” reports the CDC. “A number of biologic abnormalities have been identified in people with CFS.”
One common symptom of CFS is unrefreshing sleep. This can make it hard to distinguish the syndrome from a group of sleep disorders known as “hypersomnias.”
A new study identified DNA from a virus in 67 percent of people with chronic fatigue syndrome.
The “XMRV” virus was found in the blood of 68 out of 101 CFS patients; it was found in only eight of 218 healthy controls. The same virus has been linked to prostate cancer, Reuters reports.
“I think this establishes what had always been considered a psychiatric disease as an infectious disease,” study co-author Dr. Judy Mikovits told the New York Times.
The CDC reports that CFS involves an “all-encompassing” fatigue that is severe and incapacitating. The fatigue fails to improve with bed rest; it persists for six months or more.
Another common symptom is unrefreshing sleep. This can make it hard to distinguish CFS from a group of sleep disorders known as “hypersomnias.”
These sleep disorders all involve excessive daytime sleepiness. This sleepiness is not caused by disturbed sleep or a lack of sleep.
Narcolepsy may be the most well-known type of hypersomnia. It involves repeated episodes of daytime naps; sudden and irresistible “sleep attacks” may occur in unusual situations. Research suggests that narcolepsy is an autoimmune disorder.
Sleep paralysis and hallucinations also are common in people with narcolepsy. Another common symptom is “cataplexy.” This occurs when the leg, arm or face muscles suddenly become weak. It is normally caused by strong emotions.
People with idiopathic hypersomnia with long sleep time sleep for 10 hours or more. They also take long naps for three hours of more. Despite all of this sleep, they still feel unrefreshed.
Idiopathic hypersomnia also occurs without long sleep time. In this case you sleep for about six to 10 hours and take long, unrefreshing naps.
Recurrent hypersomnia involves repeated episodes of excessive daytime sleepiness. These may last for a few days or several weeks. You may sleep for 16 to 18 hours per day; then you sleep for normal lengths of time after an episode ends.
A common complaint of people with hypersomnia is, “I can’t wake up in the morning.” Even multiple alarm clocks may fail to wake you up. This topic has generated more than 175 replies in the discussion forum at SleepEducation.com.
Severe hypersomnia can make it difficult for you to function normally during the day; as a result your work or school performance may suffer.
A new U.K. study was unable to reproduce recent findings that suggested chronic fatigue syndrome may be linked to a virus. But U.S. researchers emphasized that there are key differences between the studies.
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