Berkeley -- People who smoke have a greater risk of becoming infected with tuberculosis (TB) and of having that infection turn into active TB disease, according to an analysis by researchers at the University of California, Berkeley.

The authors of the study, published in the Feb. 26 issue of the journal Archives of Internal Medicine, analyzed 24 studies that included details about smoking and TB outcomes. They found that smokers have a 73 percent greater chance of becoming infected than do non-smokers. For those who are infected, the chances of developing active TB disease are about 50 percent greater in smokers, compared with non-smokers. Overall, a smoker has about a 2.5 times greater risk of contracting active TB than does a non-smoker in the same population.

"Our study is the first systematic, quantitative assessment of TB risks from smoking," said lead author Michael Bates, adjunct professor of epidemiology at UC Berkeley's School of Public Health. "There have been mixed opinions on whether smoking has any relevance to TB. Our review and analysis of the research in this area indicates that there is a connection, and that smoking is a major risk factor for TB."

The results indicate that TB control policies should incorporate tobacco control as one of the preventive interventions, the researchers said.

According to the World Health Organization (WHO), nearly 2 billion people, or one-third of the world's population, are infected with Mycobacterium tuberculosis, the bacteria responsible for TB. The bacteria can remain latent in the body for decades, kept in check by a normal immune system. However, if the immune system becomes compromised, the bacteria can multiply and cause active TB disease.

"Active TB is often fatal, particularly if left untreated," said Kirk Smith, UC Berkeley professor of environmental health sciences and senior author of the paper. "The risk factors that lead to latent TB infection becomin
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Contact: Sarah Yang
scyang@berkeley.edu
510-643-7741
University of California - Berkeley
26-Feb-2007