Fat-free body mass tied to emphysema outlook

NEW YORK (Reuters Health) – Among people with chronic
obstructive pulmonary disease (COPD), usually emphysema, a low
fat-free body mass index appears to be associated with greater
mortality, Danish and UK researchers report.

There is a clear association between decreasing body mass
index (BMI) and mortality both in the general population and in
those with COPD, Dr. Jorgen Vestbo of Hvidovre Hospital and
colleagues note. They say that, in general, the harmful effect
of a low BMI is due to the low fat-free component of body mass.

The researchers point out that fat mass is a “metabolic
inactive energy source,” but fat-free mass “contains the
metabolic active organs, skeletal muscle being the largest of
these organs.”

As they put it, “It seems biologically reasonable to assume
that loss of or a low fat-free mass is unfavorable.”

To determine the association between fat-free body mass
index distribution and COPD prognosis, the researchers used
data from almost 1900 COPD patients who were followed for an
average of 7 years.

In those with a normal BMI, 26 percent had a fat-free body
mass index lower than that in the lowest 10 percent of the
general population, the researchers report in the American
Journal of Respiratory and Critical Care Medicine.

BMI and fat-free body mass index were associated with the
likelihood of dying during the study period. The mortality rate
was 57 percent among those with a fat-free body mass index
below the 10th percentile, compared with 32 percent for those
with a higher fat-free body mass index.

In light of these findings, the researchers conclude that
“assessment of fat-free body mass provides important
information in COPD and should be considered in the routine
evaluation of patients with this condition.”

SOURCE: American Journal of Respiratory and Critical Care
Medicine, January 1, 2006.