Efficacy of Cognitive Behavioral Therapy for Adolescents With Chronic
Fatigue Syndrome: Long-term Follow-up of a Randomized, Controlled Trial
Knoop et al. (1 March 2008) [Abstract] [Full text] [PDF]
Efficacy of Cognitive Behavioral Therapy for Adolescents With Chronic
Actometer readings would have provided more objective data 1 April 2009
Tom P Kindlon,
This is an interesting study. However, the issue of the use of appropriate
outcome measures is an important one in the area of Chronic Fatigue Syndrome
(CFS) research. Problems have been reported with the use of self-report
An earlier Nijmegen team incl. Gijs Bleijenberg (one of the co- authors)
investigated this area: "It is not clear whether subjective accounts of
physical activity level adequately reflect the actual level of physical
activity. Therefore the primary aims of the present study were to assess
actual activity level in patients with CFS to validate claims of lower
levels of physical activity and to validate the reported relationship
between fatigue and activity level that was found on self- report
questionnaires. In addition, we evaluated whether physical activity level
adequately can be assessed by self-report measures. An Accelerometer was
used as a reference for actual level of physical activity.". The authors
reported on the correlations on 7 outcome measures in relation to the
actometer readings: "none of the self-report questionnaires had strong
correlations with the Actometer. Thus, self-report questionnaires are no
perfect parallel tests for the Actometer." The authors pointed out that "the
subjective instruments do not measure actual behaviour. Responses on these
instruments appear to be an expression of the patients' views about activity
and may be biased by cognitions concerning illness and disability." This was
re-iterated in another paper from a different Nijmegen team involving Gijs
Bleijenberg: "In earlier studies of our research group, actual motor
activity has been recorded with an ankle-worn motion-sensing device
(actometer) in conjunction with self-report measures of physical activity.
The data of these studies suggest that self-report measures of activity
reflect the patients' view about their physical activity and may have been
biased by cognitions concerning illness and disability."
It is thus disappointing that in this current study actometers were not
either not reported or not used following the intervention. The authors do
report that they had used actometers before the intervention: "In the
original trial, 2 treatment protocols were used: 1 for patients with a
passive physical activity pattern and 1 for relatively active patients. The
physical activity pattern of the adolescent patient with CFS was measured
with an actometer, a motion-sensing device attached to the ankle."
A recent uncontrolled study highlights the problems that can occur with
self-report measures following CBT for CFS. It involved testing a form
Cognitive Behavior Therapy (CBT) for CFS which included encouraging patients
to go for longer walks. It found that on the SF-36 Physical Functioning (PF)
scale, patients improved from a pre-treatment mean (SD) of 49.44 (25.19) to
58.18 (26.48) post-treatment, equivalent to a Cohen's d value of 0.35. On
the Fatigue Severity Scale (FSS), the improvement as measured by the cohen's
d value was even great (0.78) from an initial pre- treatment mean (SD) of
5.93 (0.93) to a 5.20 (0.95) post-treatment.
However on actigraphy there was actually a numerical decrease from a
pre-treatment mean (SD) of 224696.90 (158389.64) to 203916.67 (122585.92)
post-treatment (cohen's d: -0.13). So just because patients report lower
fatigue and better scores on the SF-36 PF scale, it does not mean they are doing more, which is what GET and CBT based on GET claim to bring about.
These results seem particularly pertinent given two of the three primary
outcome measures in this study are the SF-36 PF scale and a fatigue scale.
Being able to work full-time probably involves a reasonable test of
However the usefulness of CBT to bring about improvement in hours worked is
far from clear. For example, another Dutch study of CBT reported a recovery
rate of 37%. It used the following definition for recovery: "Patients
were defined as being CSI at post treatment if they had a reliable change
index > 1.96 on the CIS fatigue severity subscale, a fatigue severity score
<= 35 and a Rand-36 physical functioning score > = 65". However, the
improvement with regards to hours worked was much smaller. Before the
intervention, participants worked an average of 9.4 hours (standard
deviation: 13.5); after the intervention, they worked 11.4 hours (standard
deviation: 14.7), a non- significant change. The median number of contracted
hours before the intervention was 10 hours; after it was 7 hours. In the
discussion section, the authors point that fewer participants had a paid job
following the intervention than before.
Attendance at school is probably not as good a measure of functioning as
hours worked. Education systems do not generally base assessments of a
child's performance on the number of days they attend! Instead, they use
measures such as outcomes in examinations. Charities for ME and CFS can
encourage some children that some sort of education at home may be more
beneficial for both their health and also their education than attendance
at school. CBT can encourage school attendance but by itself, attendance at
school should not necessarily be seen as successful result in itself if, for
example, the children are not learning that much or are under-performing
relative to their ability.
However if, as the authors may do, one believes that full attendance at
school is a good measure of activity and functioning, it would have been
good if the paper had presented data on the number and/or percentage of
participants who had "clinically significant improvement" on all three of
the outcome measures. As I pointed out earlier, following CBT, CFS patients
who report lower fatigue and/or better physical functioning may not actually
be doing more. Similarly, participants could be attending work or school
full-time but still have ongoing problems with fatigue.
It is slightly disappointing that we did not see some data: "Data on the
type of activities of patients at the time of the follow-up assessment were
not available for all of the patients. Some patients only indicated on the
questionnaires that they did not study and did not work. We decided not to
impute these missing values, because more detailed information about their
activities were lacking. This could have introduced a bias when determining
the long- term effects of CBT on work and/or school attendance. An example
of such a bias would be that these patients are less active and function at
a lower level than the patients who indicated that they worked or attended
school, which, in turn, might have led to an overestimation of the effect of
CBT." Should we assume from this that the percentage with full school/work
attendance following CBT is not 29/42 but 29/50 (58%), the same number as at
the final assessment following CBT? Data for 50 participants at follow -up
was available for fatigue severity and physical functioning.
One further point to raise is the thresholds for "clinically significant
improvement". For CIS-fatigue, it was a "reliable change index of >1.96 and
a score of <35.7". Another CBT study in the area co-written by the two of
the authors (Knoop & Bleijenberg) referred to a "normal group of 53
healthy adults with a mean age of 37.1 (SD 11.5)" who had "a mean score on
the CIS-fatigue of 17.3 (SD 10.1).". The threshold in the current study
of 35.7 is 1.82 standard deviations above that mean of 17.3. It should also
be remembered that the minimum score on the CIS-fatigue scale is 8 so that
17.3 is only 0.92 standard deviations above that. Somebody with a fatigue
score in the 30s for example still has significant fatigue.
The same study by two of the authors said that "healthy adults without a
chronic condition" had "a mean score of 93.1 (SD 11.7)" on the SF-36
physical functioning subscale. The maximum one can score is 100. Compare
that with the threshold of 75 that is sufficient to be seen as having a
"clinically significant improvement" on that scale in the current study.
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Conflict of Interest:
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