Research Briefs

Following is news of current publications and research efforts underway related to chronic fatigue syndrome (CFS), also called chronic fatigue and immune dysfunction syndrome (CFIDS).

Herpesviruses and CFS
A Centers for Disease Control and Prevention study published in the July issue of Clinical Infectious Diseases found that the human herpesviruses (HHV) 6 and HHV-7 are not likely to cause CFS, in contrast to other studies. 

The study looked at 26 CFS patients and 52 non-fatigued matched controls. The researchers used serum samples, lymphocyte assays and three different polymerase chain reaction (PCR) methods to identify the viruses.

All patients and control subjects tested positive for HHV-6, although the antibody titer was not significantly different between patients and controls. Neither HHV-6 nor HHV-7 was isolated from peripheral blood lymphocytes of patients or control subjects, a sign that no active infection or viral reactivation was involved.

HHV-6 (A or B) DNA was detected in 17 (22.4%) of 76 samples and there were no significant differences between patients and control subjects. HHV-7 DNA was detected in 14 subjects. Although the controls (24%) were more likely than patients (7.7%) to be positive for HHV-7, the difference was not statistically significant.

The researchers concluded that there was no evidence active or latent infection with HHV-6A, HHV-6B, HHV-7 or any combination of these viruses is associated with CFS. At least seven other studies on HHV-6 or HHV-7 infection and CFS have been published, and reported widely differing results, but it is difficult to compare them with the CDC’s study because of the different methodologies used.

Reeves et al. Human herpesviruses 6 and 7 in chronic fatigue syndrome: a case-control study. Clin Inf Dis. 2000; 31: 48-52.

Response to exercise
A study conducted by St. Bartholomew’s and the Royal London School of Medicine and Dentistry has shown that CFS patients have a significantly reduced exercise capacity (see also article on exercise intolerance in this issue).

Researchers measured the strength, aerobic capacity and functional capacity of 66 CFS patients who had not been diagnosed with a psychiatric disorder, 30 healthy but sedentary controls and 15 patients with major depressive disorders. Exercise capacity and efficiency were assessed by monitoring peak and submaximal oxygen uptake, heart rate, blood lactate, duration of exercise and perceived exertion during a treadmill test.

The study found that the CFS patients were physically weaker than the sedentary and depressed controls and as unfit as the sedentary controls. They also showed lower aerobic capacity and lower maximum heart rate than the controls.

The researchers speculate that improved physical fitness after exercise therapy was associated with increased exercise capacity and that a program to reverse deconditioning may help improve physical functioning in some patients.

Fulcher KY and White PD. Strength and physiological response to exercise in patients with chronic fatigue syndrome. J Neurol Neurosurg Psychiatry. 2000; 69: 302-7.

Co-morbidity of CFS, FM and MCS
Many of the symptoms associated with CFS are also characteristic of other poorly understood medical conditions, including fibromyalgia (FM) and multiple chemical sensitivities (MCS). A study from DePaul University has examined illness co-morbidity rates for the three illnesses as well as characteristics related to fatigue severity and disability.

Thirty-two individuals with symptoms of CFS received medical and psychiatric evaluations to confirm the diagnosis. Of the 32, 40.6% met criteria for MCS and 15.6% met criteria for FM. Thirteen of the 32 (40.6%) had CFS without any other coexisting illness.

These rates for coexisting disorders are lower than those reported in prior studies; the researchers speculated that the discrepancy may in part be the differences in sampling procedures.

The researchers noted that having co-morbid conditions does affect a patient’s functionality. Individuals with more than one diagnosis reported more mental and physical fatigue than those with no diagnosis and were less likely to be working.

Jason LA et al. Chronic fatigue syndrome, fibromyalgia, and multiple chemical sensitivities in a community-based sample of persons with chronic fatigue syndrome-like symptoms. Psychosomatic Med. 2000; 62:655-63.

More evidence of OI involvement
Researchers from the State University of New York Health Sciences Center have provided additional evidence that delayed orthostatic intolerance (OI) is an important physical disorder found in many patients with moderate to severe CFS.

The blood pressure, heart rate and circulating erythrocyte and plasma volumes of 15 CFS patients were measured every minute for 30 minutes supine and 60 minutes standing. Eleven of the 15 showed excessive reductions in systolic and diastolic blood pressure, orthostatic tachycardia and presyncopal symptoms after standing for 60 minutes. None of the controls showed symptoms of OI.

In addition, circulating erythrocyte volumes were subnormal in 12 of the 14 CFS patients and plasma noriepinephrine concentration rose excessively after standing for 10 minutes. Lower body compression with MAST (military antishock trousers) restored all orthostatic measurements to normal and overcame presyncopal symptoms within 10 minutes in the CFS patients.

Streeten DH and Bell DS. The roles of orthostatic hypotension, orthostatic tachycardia, and subnormal erythrocyte volume in the pathogenesis of chronic fatigue syndrome. Am J Med Sci. 2000; 320:1-8.