Factor analysis of unexplained severe fatigue and interrelated symptoms: overlap w/ criteria for CFS

[Dolphin]

Am J Epidemiol. 1998 Jul 1;148(1):72-7.
Factor analysis of unexplained severe fatigue and interrelated symptoms: overlap with criteria for chronic fatigue syndrome.

Nisenbaum R1, Reyes M, Mawle AC, Reeves WC.


Abstract

The objective of this study was to identify factors explaining the correlations among unexplained severe fatigue of different durations (1-5 months or > or =6 months) and symptoms reported as being significant health problems during a preceding 4-week period.

Between June and December of 1994, a cross-sectional, random digit dialing telephone survey was conducted among residents of San Francisco, California.

All subjects who reported having severe fatigue lasting for > or =1 month and a random sample of nonfatigued subjects were asked to participate in a detailed telephone interview.

Data from 1,510 individuals aged 18-60 years who did not have medical or psychiatric conditions that could explain their severe fatigue were analyzed.

Common factor analyses identified three correlated factors (defined as "fatigue-mood-cognition" symptoms, "flu-type" symptoms, and "visual impairment") that explained the correlations among fatigue lasting for > or =6 months and 14 interrelated symptoms.

No factor explained the correlations among fatigue lasting for 1-5 months and other symptoms.

The combination of fatigue of > or =6 months' duration and selected symptoms overlaps with published criteria used to define cases of chronic fatigue syndrome (CFS).

Although symptoms described in this study were reported as appearing within the preceding month, and CFS symptoms must have been present for the previous 6 months, these results provide empirical support for the interrelations among unexplained fatigue of > or =6 months' duration and symptoms included in the CFS case definition.

PMID: 9663406
[Indexed for MEDLINE]

 

[Dolphin]

I've read this but I'm still not sure whether it really tells us anything about what symptoms should be used to define ME/CFS. Given that some cases of chronic debilitating fatigue will be due to other things (apart from the exclusions they used), it seems to me like all this found was what symptoms go together in those who have fatigue six months or longer, but I could be wrong.

 

[Dolphin]

 

[anciendaze]

This kind of study always suffers from a problem because it confounds two things: 1) an illness suffered by patients, 2) common thinking habits of doctors. Byron Hyde argues that there is no such disease as "Chronic Fatigue Syndrome" (CFS), only Myalgic Encephalomyelitis (ME), caused by enteroviruses, and misdiagnosis. I wouldn't go that far, (I have my suspicions about herpes viruses like HHV6a,) but I have to admit that in operational terms for vast numbers of doctors CFS means some vague chronic condition with a lot of fatigue, and a label which will get them out of my clinic. As long as such thinking persists we will find any number of disparate conditions dumped into a common wastebasket, and this will confound research and treatment.

By a series of chance experiences in the past I have encountered several people with rare conditions that have happened to get swept up in the CFS basket. These include infectious, genetic and autoimmune diseases -- a wide range of causes. I will even admit that most such conditions are quite rare in clinical practice. What I will not admit is that ignoring conditions in a particular patient because they are rare in others is acceptable medical practice when you a labeled as a professional and patients are paying for something more than the generic treatment advice they could get from a television program.

Over and over again, I have been confronted with medical treatments that don't work, and doctors who persist in using them on all patients because they might work on some. If you don't pay attention to evidence your treatment option is not working in a particular patient you can do great harm, but as long as doctors are paid merely for treatment the motivation to discover that a treatment is ineffective is weak.

This is not simply a problem for treating minor chronic conditions that are never fatal. Here is a report on new drugs prescribed to treat cancer which shows that the majority licensed for clinical practice don't actually provide the benefits expected. Something is seriously wrong with a system that functions this poorly when dealing with life-threatening illness. Is it any wonder such a broken system functions more poorly in handling chronic conditions that are rarely fatal?

In addition, I want to point out that most cancer patients go through a prodromal phase when cancer affects their performance and general health but is not specifically indicated by clinical signs. More than one such patient has ended up with the label CFS, and this delays diagnosis and treatment of actual cancer.

 

[Sean]

In addition, I want to point out that most cancer patients go through a prodromal phase when cancer affects their performance and general health but is not specifically indicated by clinical signs.

I suspect this is true for a lot of ME patients as well. The sudden v. gradual onset always seemed to me more an artifact of poor methodology than a distinct feature.

 

[Snow Leopard]

These factor analyses just reveal the lack of specificity of the measures used.