Second-hand smoke tied to asthma severity

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," said lead investigator Dr. Mark D. Eisner. "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.

Asthma is an inflammatory disorder of the airways, characterized by periodic attacks of wheezing, shortness of breath, chest tightness, and coughing.

Causes, incidence, and risk factors

Asthma is a disease in which inflammation of the airways causes airflow into and out of the lungs to be restricted. When an asthma attack occurs, the muscles of the bronchial tree become tight and the lining of the air passages swells, reducing airflow and producing the characteristic wheezing sound. Mucus production is increased.

Most people with asthma have periodic wheezing attacks separated by symptom-free periods. Some asthmatics have chronic shortness of breath with episodes of increased shortness of breath. Other asthmatics may have cough as their predominant symptom. Asthma attacks can last minutes to days, and can become dangerous if the airflow becomes severely restricted.

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 ."