Longitudinal study of physical activity & BMI among persons with unexplained CF -2005

[Dolphin]

93% of the patients in this study actually had CFS. It's disappointing they didn't simply use their data and make it a CFS paper

This isn't particularly exciting but I just read it and thought I'd post the info somewhere.

A longitudinal study of physical activity and body mass index among persons with unexplained chronic fatigue.

J Psychosom Res. 2005 Apr;58(4):375-81.

Schmaling KB, Fiedelak JI, Bader J, Buchwald D.


Source

College of Health and Human Services, University of North Carolina, Charlotte, NC 28223, USA. kbschmal@email.uncc.edu


Abstract

OBJECTIVE AND METHODS:

A cohort of 100 patients with unexplained chronic fatigue (CF) was assessed longitudinally for 1.5 years to determine if physical activity (kcal expended), exercise capacity (VO(2)max), perceived exertion, and body mass index (BMI) changed over time and were associated with changes in CF-related clinical status.

RESULTS:

BMI increased significantly over time but did not predict changes in clinical status.

Increasing energy expenditure was associated with increasing vitality and decreasing CF symptom severity over time, and decreasing perceived exertion was associated with increasing physical functioning.

However, increasing perceived exertion was also associated with increasing CF symptoms.

CONCLUSIONS:

These data do not support models that posit associations between CF and deconditioning.


PMID: 15992573 [PubMed - indexed for MEDLINE]

 

[Dolphin]

Aside - interesting given the PACE Trial authors to claim scores of 60+ were in the normal range:

The Medical Outcomes Study Short Form-36 (SF-36;
[21] ) was used to evaluate functional status. This 36-item
questionnaire consists of eight scales that reflect physical
functioning, role -physical functioning, role -emotional
functioning, social functioning, mental health, bodily pain,
vitality, and health perceptions. Higher scores indicate better
functioning (range, 0100), with the normal range considered
to be 80 and above.

 

[Dolphin]

The general linear mixed model analysis for the effect of elapsed
days on the predictor variables revealed that BMI increased
significantly over time [t(257)=3.31, P<.01; 354 observations
available for analysis], such that the passage of a year
was associated with an increase in BMI of 0.30 units.

This isn't clear at all from Table 1 but presumably is to do with missing values.
They give little figures of the progression of every patient - one figure when the BMI went up and one when it went down. Not particularly exciting but there is only one big change: one person's BMI went from just under 45 to around 30: I'm guessing they either went on a brilliant diet or else had some sort of surgery.

The change in BMI probably isn't that interesting as they later say:

The annual rate of increase in BMI among the participants
in this study (0.30) was greater than that observed in a longterm
longitudinal study of the natural history of weight gain
among Caucasian women (0.25; [34] ).

 

[Dolphin]

What attracted me to this paper was that they said it disproved the deconditioning there.

Here's what they found on this:

For CF symptom severity, a total of 274 observations
was available, and the overall test was significant
[F (4,219)=6.65, P<.001]. Decreasing symptom severity
was associated with decreasing VO2max [an increase of 1.7
points of CF symptom severity for each l/min increase in
VO2max; t(263)=2.41, P<.05], decreasing RPE [a decrease
of 0.3 CF symptom severity points for each unit decrease in
perceived exertion; t (269)=3.09, P<.01], and greater energy
expenditure [a decrease of 0.001 CF symptom severity points
for each additional kcal expended; t(262)=2.00, P<.05].

For the SF-36 physical functioning subscale, 278
observations were available for analysis, and the overall
test was significant [F (4,234)=6.64, P b.001]. Over time,
decreasing physical functioning was associated with
increasing VO2max [a decrease of 1.6 points on the physical
functioning scale for each l/min increase in VO2max;
t (270)=2.18, P b.05] and increasing perceived exertion
[a decrease of 0.45 points in physical functioning for each
unit increase in RPE; t(257)=4.29, P b.001].

(energy expenditure was not measured objectively but using a questionnaire asking about activity levels)

As noted earlier, this sample demonstrated an oxygen
uptake that was below normal. Although CFS patients might
be expected to be deconditioned, these data do not support an
association between CF and deconditioning (e.g., Refs.
[2,4]), as our most direct measure of exercise capacity,
VO2max, demonstrated an unexpected longitudinal association
with clinical status. If deconditioning was the result of,
or resulted in, CF, one would predict increased CF symptoms
and decreased physical functioning as conditioning worsened.
However, physical conditioning worsened (oxygen
uptake decreased) as CF symptom severity and physical
functioning measures improved.

 

[Dolphin]

BMI

Although BMI increased over time in this study, and we previously reported
that vitality increased over time [30], BMI did not predict
changes in vitality or other clinical outcomes. Similarly, in
their longitudinal study of fibromyalgia, Mengshoel and
Haugen [35] observed that patients gained weight but
reported less pain and fatigue over time. However, greater
BMI was associated with worsened fatigue at a 2-year
follow-up among persons with ICF [6], and being overweight
or obese has been correlated with poorer physical
functioning and vitality in a population-based study [36].
Further studies to clarify the longitudinal associations
between BMI and clinical changes in CF are warranted.

and

In conclusion, weight gain was not associated with poorer
clinical outcomes. With nearly 300 observations, it is
unlikely that the lack of statistically significant associations
of BMI with clinical outcomes was due to a lack of power.

There is some speculative stuff in the paper e.g. gaining weight is bad, people should try to lose weight and exercise programs might help as they have shown to work, but I can't copy everything and I'm not sure there's anything too conclusive in this paper anyway.