Orthostatic Intolerance may play role in chronic fatigue syndrome
Scientific panel issues consensus statement calling for more research

Orthostatic intolerance (OI), a condition in which upright posture provokes dramatic changes in heart rate and blood pressure, may have a connection to chronic fatigue syndrome (CFS). This was one conclusion reached by a panel of experts that convened in December 2000 for the first in a series of scientific symposia on CFS sponsored by The CFIDS Association of America.

OI is an umbrella term for several disorders that may be due in part to abnormalities in the autonomic nervous system. The connection between OI and CFS was first explored in 1995, when researchers at Johns Hopkins University identified at least one form of OI in 96% of CFS patients tested.

"The field of OI is one of the most promising avenues for gaining more insights into CFS," said panel chair Tim Gerrity, executive director of the Chronic Pain & Fatigue Research Center at Georgetown University. "Conducting more research on the similarities between the two conditions could directly benefit the millions of people worldwide who live with this devastating illness."

Following a day of presentations and discussion by experts, an independent panel composed of well-respected researchers and practitioners in the fields of endocrinology, epidemiology, pediatrics, rheumatology, neurology, psychology, allergy and internal medicine developed a consensus statement on the key issues surrounding CFS and OI. This statement was published in the December 2002 issue of NeuroImmune Modulation.

The panel agreed that:

• There is evidence of an altered autonomic nervous system and/or circulatory system in CFS. The panel noted that the symptoms of OI are often seen in CFS patients and that the physiological stressors that exacerbate OI may also intensify symptoms in CFS patients.
• The exact relationship between OI and CFS is still unclear. Although both conditions may be preceded by a viral-like illness, patients with OI (but not CFS) often do not report hallmark symptoms of CFS, including severe fatigue, post-exertional malaise, joint and muscle pain, recurrent sore throat and painful lymph nodes.
• Methods for studying autonomic nervous system dysfunction in CFS are available. Although a number of conditions such as OI, Addison's disease and acute Epstein-Barr infection have clinical features in common with CFS, there are no human models that sufficiently reflect the spectrum of CFS symptoms. However, the panel pointed out that animal models and tests measuring the patient's response to a specific activity or pharmacologic challenge can be used to study aspects of autonomic regulation in CFS.
• There are relationships between autonomic nervous system dysfunction and other abnormalities seen in CFS patients. The available data suggest that CFS patients have altered relationships between the autonomic nervous system and the cardiovascular, neuroendocrine and immune systems. The panel recognized that the extensive interdependence of these systems has made discovery of a primary cause of CFS a constant challenge for the research community.
• More research is needed to further define the possible interaction between OI and CFS. The panel outlined future research needs, including more studies of autonomic function and altered brain perfusion, examination of the relationships between the autonomic nervous system and other body systems, and testing of therapeutic interventions to directly impact patient care in CFS. The panel also suggested ways to overcome some of the methodological barriers researchers have faced, including subgrouping CFS patients to handle the diversity of the patient base and using standard definitions of OI terms to ensure that future study results can be compared.

The CFS assessment symposia series is designed to examine the role of the endocrine, circulatory and immune systems in CFS. The symposia gather experts to evaluate research findings, identify the most promising next steps for research, define research and funding priorities, and create research collaboration teams.

The CFIDS Association of America is the nation's leading organization working to conquer this illness. Since 1987, the Association has invested over $12 million in education, public policy, and research programs in its efforts to bring an end to the suffering caused by CFS.

CFS, also called chronic fatigue and immune dysfunction syndrome (CFIDS), is defined as a debilitating and complex disorder characterized by profound fatigue, pain, and cognitive problems not improved by bed rest and that may be worsened by physical or mental activity. Persons with CFS function at a substantially lower level of activity than they were capable of before the onset of the illness.

ANS Symposium Literature Review