Smoking may increase the risk of tuberculosis, say researchers at the University of California, Berkeley, who analysed data from 24 previously published studies on the subject.
The meta-analysis found that, compared to non-smokers, people who smoked were 73 percent more likely to become infected with TB and more than twice as likely to develop active TB.
Risk significantly increased
Overall, smokers are 40 percent to 60 percent more likely than non-smokers to develop TB after being infected with TB bacteria, the researchers said.
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The findings were published in the February 26 issue of the Archives of Internal Medicine.
About a third of the world's population is infected with TB bacteria, usually rendered inactive by the immune system. In 2003, active TB developed in about 8.8 million people worldwide. The disease kills about 1.7 million people a year, according to background information in the study.
There may be several reasons for the association between smoking and TB. Smoking may decrease immune response or damage the protective effect of tiny hair-like structures called cilia in the airways, resulting in increased TB risk.
"Tuberculosis control policies should in the future incorporate tobacco control as a preventive intervention," the review authors wrote.
A modifiable risk factor
"Potentially, smoking is one of the most modifiable of exposures. In developing countries, where life expectancy is short, highlighting smoking as a risk factor for TB may have greater resonance than advertising its risks for cancer and cardiovascular disease," they concluded.
The review authors also found that the increased risk of death from TB associated with smoking was less than the increased risk of getting TB disease. The authors said this suggests that smoking doesn't increase the risk of death in people who already have active TB. – (HealthDayNews)
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