Death risk higher in women on oxygen for COPD

NEW YORK (Reuters Health) – Women on oxygen therapy for
severe chronic obstructive pulmonary disease (COPD) have a
greater risk of dying than men, according to a prospective
study of 435 oxygen-dependent COPD patients.

COPD, a progressive lung illness often caused by smoking
that includes emphysema and chronic bronchitis, is
characterized by airflow limitation that is not fully
reversible. People with severe COPD often require continuous
oxygen therapy.

Dr. Maria-Christina L. Machado of the State Public Hospital
in Sao Paulo Brazil and colleagues followed 184 women and 251
men receiving oxygen therapy over seven years.

They observed that the “hazard ratio” for death was
markedly higher in female subjects relative to male subjects,
after adjusting for age, smoking history, lung function and
body weight.

Men and women exhibited similar survival rates during the
initial follow-up period; survival differences became more
apparent only after three years of follow up.

In an editorial on the research, Dr. David M. Mannino of
the University of Kentucky Medical Center suggests that “one
explanation for the worse survival among women might be that
some of the systemic complications of COPD, such as muscle
dysfunction or depression, are more common in women and that
these lead to worse outcomes.”

In two recent studies of COPD patients, the prevalence of
depression was nearly three times higher in women as men (38
percent vs 13 percent) and the prevalence of fat-free body mass
depletion was twice as high (40 percent vs 20 percent), Mannino
notes.

“While we do not know whether these complications were
increased in the study by Dr. Machado and colleagues, it is
plausible that the observed differences may have been related
to these or other COPD-related complications that differ
between the sexes,” Dr. Mannino writes.

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