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Monday, December 3, 2001

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Chemicals linked to chronic fatigue

By Julie Robotham, Medical Writer

Chronic fatigue syndrome (CFS) could be caused by common chemicals such as head lice treatments and insect repellents, a United States expert has told a Sydney conference.

The condition, which affects up to one in 250 adults, has been derided as "yuppie flu" or dismissed as a psychological illness, but doctors are now in general agreement that it is real, an international conference on CFS at Manly heard at the weekend.

Chemicals that were relatively harmless when used independently of each other could become highly toxic to the brain when used together, said Mohamed Abou-Donia, a professor of pharmacology, cancer biology and neurobiology at Duke University Medical Centre.

Rats suffered cell death in the areas of the brain controlling movement and memory when they were exposed through their skin to DEET, used in insect repellents, and permethrin, a popular insecticide, Professor Abou-Donia said. This was "consistent with muscle weakness, joint pain and problems with the central nervous system" reported by CFS patients.

Professor Abou-Donia also presented research which showed that rats were more susceptible to such chemical exposures if they were also under stress. Stress seemed to "cause minor breakdown of the blood-brain barrier", allowing chemicals to permeate the brain more easily.

"It seems to me that CFS and Gulf War syndrome have many common characteristics," Professor Abou-Donia said.

He said governments should consider restricting the availability of some household chemicals until more was known about their interaction in the brain with each other and with other substances such as over-the-counter medicines.

A director of general medicine from Harvard Medical School, Anthony Komaroff, said there was "a preponderance of evidence that a variety of abnormalities - objective biological abnormalities - are present" in the brains of CFS patients.

As well, Professor Komaroff said CFS usually involved the activation of the immune system. The fact that twice as many women as men were diagnosed with the condition lent additional weight to the hypothesis that CFS was essentially an immune disorder because all immune diseases, including lupus and rheumatoid arthritis, affected females more frequently than males.

Emerging evidence had also linked CFS to human herpes virus 6, which causes the childhood illness roseola, and to enteroviruses, which could persist in the body indefinitely.

Cognitive behaviour therapy and exercise regimes could help people deal with their illness, Professor Komaroff said, but for those who were most sick, exercise was counter-productive and exacerbated their illness.

Wilhelmina Behan, professor of muscle pathology at Scotland's Glasgow University, said she had collected more than 100 muscle biopsies from people with CFS, and would now analyse them in an attempt to identify any common genetic variations that might make people susceptible.

She said normal muscle tissue was made up of two types of fibres: "fast" fibres, which were used for bursts of activity, and "slow" fibres, associated with endurance tasks. People with CFS had up to 20 per cent fewer slow fibres, she said, which explained why they tired easily

© 2001The Sydney Morning Herald
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