Second-hand smoke tied to asthma severity

By David Douglas

NEW YORK (Reuters Health) – Exposure to second-hand tobacco
smoke appears to increase asthma severity and might even
influence the risk of hospital admission, according to a new
report.

“Our study showed that second-hand tobacco smoke can be
harmful for adults with asthma,” lead investigator Dr. Mark D.
Eisner told Reuters Health. “These results provide further
justification for banning smoking in public places.”

Eisner of the University of California, San Francisco and
colleagues note that most previous studies of asthma and
passive smoking have relied on self-reported exposure.

In the present study, published in the journal Thorax, the
researchers used nicotine badges to measure exposure. The
badges trap ambient nicotine in a filter, and gas
chromatography is subsequently used to evaluate the content.
Hair was sampled for nicotine and its major metabolite cotinine
to determine the levels of longer-term exposure.

The badges were used for seven days in 189 subjects who had
had a recent asthma hospitalization. A similar group of 138
asthmatics submitted hair samples to determine exposure in the
previous three months.

Asthma severity over these time periods was established by
telephone interviews.

Most of the subjects were exposed to second-hand smoke,
with estimates ranging from 60 percent to 83 percent. The
highest levels of recent exposure as determined by the badge
were related to greater asthma severity.

Those with the highest levels of nicotine exposure in the
previous month appeared to be at greater risk of hospital
admission.

In an accompanying editorial, Dr. J. Britton of City
Hospital, Nottingham, UK notes that the results are consistent
with the “interpretation that individuals with higher levels of
passive smoke exposure had more troublesome asthma.”

However, “the findings on the risk of hospitalization were
perhaps less convincing.” This was due to the observational
nature of the study and the low participation rate of eligible
subjects.

Nevertheless, he concludes that “smoke exposure is likely
to be bad for all people with asthma who would be well advised
to avoid exposure, as indeed is the case for everyone else.”

SOURCE: Thorax, October 2005.