Regular tobacco smoking doubles the risk that people who have been successfully treated for tuberculosis will develop it again, a condition known as "recurrent" TB, according to a research published today.
The research provides critical insights on the harmful links between smoking tobacco and developing TB.
The study which appears in the April issue of the International Journal of Tuberculosis and Lung Disease is the most robust ever conducted into how smoking tobacco increases the risk of recurrent TB.
"More than ever before, we understand how tobacco harms people who have already been successfully treated for TB," said Dr Chung-Yeh Deng of National Yang-Ming University in Taipei, one of the authors of the study.
Nearly 2 billion people are infected with TB every year and more than 20 per cent of global TB incidence may be attributable to smoking.
"No one should undergo the long, complex treatment for TB only to unknowingly place themselves at heightened risk of getting the disease again", Deng said.
The researchers followed a large sample of 5,567 TB patients in Taiwan, each of whom had TB confirmed through bacteriologic testing and went on to successfully complete TB treatment.
Of those patients, 1.5 per cent developed a recurrent case of TB.
The report showed that regular tobacco smokers are twice as likely to develop recurrent TB compared with former smokers and with individuals who had never smoked tobacco.
Regular tobacco smokers were defined as individuals who smoked 10 or more cigarettes—equivalent to half a pack—per day.
"Until this study was published, we didn't have a clear sense of how smoking tobacco posed risks to TB patients who have put in the hard work of completing their treatment," said Dr Paula Fujiwara, Scientific Director of the International Union Against Tuberculosis and Lung Disease, which publishes the journal.
The research was announced on March 24 to coincide with World TB Day, which marks the anniversary of Prof Robert Koch's discovery of the bacteria that cause tuberculosis in Berlin.
More than a century later, Koch's discovery is still considered among the most revolutionary in the history of medicine, since it paved the way to finding a cure for the disease known in the 19th century as "The White Plague".
"You often see tuberculosis still referred to as an 'ancient' disease, but this study is further evidence that TB is a fully modern illness that is impacting people in new ways," said José Luis Castro, Interim Executive Director of The Union.