Etiology, Exercise and CFS -Suzanne Vernon, Phd

[Guest guest]

Reference:

Etiology of Chronic Fatigue Syndrome: Testing

Popular Hypotheses Using a National Birth Cohort

Study - see abstract, posted by Fred Springfield at

Co-Cure:

http://listserv.nodak.edu/cgi-bin/wa.exe?A2=ind0804a & L=co-cure & T=0 & P=1270

~jvr

http://www.cfids.org/cfidslink/2008/040903.asp?tr=y & auid=3544493

Etiology, Exercise and CFS

~~~~~~~~~~~~~~~~

By Suzanne Vernon, Phd

Hot off the press from the journal Psychosomatic

Medicine is a paper by B. Harvey,

Wadsworth, Simon Wessely and Hotopf

entitled " Etiology of Chronic Fatigue Syndrome:

Testing Popular Hypotheses Using a National Birth

Cohort Study. "

Despite the psychological spin they put on the

results, the findings in this paper validate what

many in the patient community describe regarding

activity levels prior to the onset of illness: " I was a

runner. . . " ; " I loved to hike. . . " ; " until I got CFS. "

This is an important publication because of that

validation. This paper also reminds us of the

importance and possible impact of events that

happen across the lifespan.

Let's first break down the title so that we understand

what the study attempts to do.

Etiology is the study of causation. Even though many

investigators have searched for the cause of CFS, it

has proven to be elusive. There have been many

explanations as to why scientists haven't pinned

down a cause, but the most likely one is that CFS is

a complex, chronic disease resulting from a

combination of gene-environment interactions.

Chronic diseases like CFS are tough to study let

alone to identify a cause because--as the name

chronic implies and the definition insists upon--the

disease occurs over time. The term birth cohort

refers to a group of people enrolled in a study from

birth and followed for a certain period to evaluate

any number of issues across the lifespan.

Three of this study's investigators are from the

Institute of Psychiatry at King's College London and

the other, Professor Wadsworth, is the

retired director of the Department of Epidemiology

and Public Health at University College London. This

is the department that operated the National Survey

of Health and Development, a British national birth

cohort survey established in 1946, originally to

investigate how lifespan health matters might affect

fertility and obstetric issues.

In this study, the investigators aimed to test a set

of hypotheses about the cause of CFS. They

examined whether there were increased rates of

allergy and asthma (referred to as atopic illness),

decreased levels of physical exercise and/or

increased childhood illnesses in people with CFS.

Since this is a birth cohort, each hypothesis tapped

into information from various ages. For example,

childhood illness was evaluated between the ages of

6 to 15 years. A history of atopic illness was taken

when the study subjects were 36 and 43 years old.

Information on physical activity was gathered across

the lifespan up to 53 years of age.

While there is a great deal of data on this cohort,

only information relevant to the above hypotheses

was analyzed. (You can read more about this cohort

and the kinds of information collected at

http://ije.oxfordjournals.org/cgi/reprint/35/1/49.pdf.)

The first step was to determine how many people in

this cohort self-reported a diagnosis of CFS. Of 2,983

participants, 10 men and 24 women (1%) reported a

diagnosis of CFS with fatigue symptoms starting

between 41 and 53 years of age.

When investigators looked at rates of childhood

illnesses that resulted in school absence or

hospitalization in these 34 people with CFS, they

were no different from the rest. There were also no

differences in the rates of atopic illness. And rather

than finding decreased levels of physical exercise,

the authors were surprised to find that the 34 people

with CFS had higher than average levels of exercise

throughout childhood and a lower body mass index

prior to their CFS diagnosis.

Interestingly, these same folks reported continued

exercise even after they began to experience early

symptoms of fatigue.

So does this study identify the cause of CFS as being

exercise? No. However, it did a reasonable job of

decreasing the possible importance of atopic illness,

lifetime inactivity or exercise phobia as causes of

CFS.

The authors also did a good job of acknowledging

some of the strengths and weaknesses of the study.

But the greatest weakness of this study (which was

not acknowledged) is using a national birth cohort

that was designed to study something else.

Since this particular British national birth cohort was

designed to study fertility and obstetric issues, the

information collected is particularly relevant to these

two health questions.

So some potentially CFS-relevant information may be

missing. For example, the information on childhood

illness is limited, and there's no information on

illnesses--in particular infectious disease

episodes--after age 15.

The information that was not collected from this

national birth cohort isn't the fault of the authors.

But rather than interpreting that the drive to be

physically active is a personality trait that

predisposes people to CFS, what might these

researchers have found if they had the information

and inclination to approach their investigation from a

gene-environment perspective?

There is sufficient evidence in the literature that

points to genetic vulnerability for CFS. There's also

extensive evidence documenting environmental

events, such as infectious mononucleosis, that can

trigger CFS.

Now we see a possible connection to body mass and

lifetime activity. So what happens to active

individuals who get the " flu " and return to that same

lifestyle after they feel they've recovered? It's time

for investigators to step out of their comfort zone

and step up to the task of connecting these

tantalizing bits of disparate information to get to the

cause(s) of CFS.