"Data from this study suggest that people suffering with these and other symptoms of CFS are likely to have a physical cause for their difficulties, even when a clear-cut medical diagnosis cannot be found" - and face increased risk for illnesses with more definitive tests & treatments.
A new study conducted by researchers from Emory University and the Centers for Disease Control and Prevention (CDC) shows that individuals with chronic fatigue syndrome (CFS) have increased blood levels of the inflammatory chemicals known to increase risk for developing illnesses ranging from cardiovascular disease and dementia to diabetes and cancer. The results of the study, published in the journal Brain, Behavior and Immunity are available on line* [no abstract available].
There has been debate over the years regarding the role played by the immune system in disorders like CFS and fibromyalgia. Such disorders have no known cause but ravage people's lives with symptoms such as fatigue, pain, sleep disturbance and troubles with thinking and memory.
"Data from this study suggest that people suffering with these and other symptoms of CFS are likely to have a physical cause for their difficulties, even when a clear-cut medical diagnosis cannot be found," says
Charles L. Raison, MD, lead author on the study and clinical director of the Mind-Body Program in the Department of Psychiatry and Behavioral Sciences at Emory University School of Medicine.
The study also showed that inflammation is not specific for CFS and so doesn't hold much promise as a diagnostic tool for CFS, Raison explains.
"We don't know where the increased inflammation is coming from in the patients with CFS symptoms in our study, and although depression has been associated with increased inflammation, in our study it did not account for the increased inflammation in individuals with CFS or who almost met criteria for CFS."
"Given these observations, the simplest way to think about these findings is that people with increased inflammation - from whatever source - are more likely than others to develop a range of symptoms that frequently lead to a diagnosis of a condition such as CFS or fibromyalgia," says William C. Reeves, MD, co-investigator of the study and chief of the Chronic Viral Diseases Branch of the Centers for Disease Control and Prevention (CDC).
Reeves emphasizes that study results may have health implications. "Because even mild increases in inflammatory markers such as c-reactive protein (CRP) have been shown to predict the later development of many serious illnesses, we might do better to see conditions such as chronic fatigue syndrome as way stations on the road to diagnosable medical illnesses rather than as a discreet disease state in its own right."
Prior studies have shown that chemicals like CRP are produced by inflammatory processes that can cause symptoms of CFS. Those studies have often been confounded by a variety of factors, such as small patient groups, recruiting patients and comparison subjects from very different populations and not carefully looking for the presence of medical and psychiatric disorders that are also associated with increased inflammation.
'We have attempted to address the shortcomings of previous studies by recruiting patients and control subjects from the same large, population-based sample of individuals, and carefully screening for the presence of conditions such as depression that frequently co-occur with CFS, and that might skew findings," says Raison.
To examine the relationship between CFS and inflammation, study investigators measured blood levels of CRP and white blood cells in 457 individuals recruited as part of a larger study on the prevalence of CFS in metropolitan, urban and rural Georgia.
Individuals in the study underwent extensive evaluations to identify medical and psychiatric conditions and to identify illnesses that are currently considered sufficient to explain fatigue and other symptoms that exclude an individual from being able to receive a CFS diagnosis.
In addition to these assessments, all individuals in the study were diagnosed either as having CFS, as having symptoms of CFS but not meeting full criteria for the disorder, or as being well.
The researchers found that subjects with CFS had higher levels of CRP than did well individuals and also had higher scores on an inflammatory factor that included both CRP and white blood cell levels.
Subjects who had CFS symptoms, such as fatigue, pain, sleep disturbance and cognitive complaints, but who did not meet full CFS criteria, also had higher levels of CRP and the inflammatory factor than did well individuals and had higher levels of white blood cell levels.
Additionally, researchers found that subjects who had symptoms but did not meet full CFS criteria had numerically higher levels of inflammation than did subjects with CFS; however, these differences were not significantly different.
Other factors associated with increased inflammation in the study population as a whole included depressive symptoms, being overweight, and being a female. Researchers found that inflammation was strongly associated with reported disability from physical symptoms in the population as a whole, but was not associated with disability from mental symptoms such as anxiety.
Jin-Mann S. Lin, PhD, from the Chronic Viral Diseases Branch of the CDC also contributed to this study.
Dr. Raison is on the speaker's bureau for Wyeth, Lilly and Schering Plough. He has served on advisory boards for Wyeth, Lilly, Schering Plough and Centocor and is a consultant for eGenHealth.
Funding for this study was provided by the Centers for Disease Control and Prevention (CDC).
"Association of peripheral inflammatory markers with chronic fatigue in a population-based sample," Brain, Behavior and Immunity, published online Dec. 2008, DOI:10.1016/j.bbi.2008.11.005