We welcome the commentary "Addressing Smoking Cessation in Tuberculosis Control" responding to the Bulletin theme issue on tuberculosis (May 2007), and thank the authors for raising this important issue.
If action is not taken to curb the spread of tobacco use, annual deaths are expected to reach 8.3 million by 2030, of which more than 80% will be in developing countries. (1) Smoking globally is about four times more common among men than women. However, trends are changing, with increasing levels among women, and girls are smoking almost as much as boys in many settings. (2) In addition, girls and boys use non-cigarette tobacco products such as chewing tobacco, bidis and water pipes at similar rates.
Many of the countries with increasing tobacco consumption are those with a high burden of TB.
Core TB control components, as advocated in the Stop TB Strategy, are intended to break the chain of mycobacterial transmission by ensuring early diagnosis and effective treatment of TB patients. However, over the past decades, global TB control strategies have paid less attention to the relative importance of different determinants and risk factors for TB, such as smoking, malnutrition, diabetes, crowding and indoor air pollution. There is a clear need to address these risk factors to reduce people's vulnerability to TB infection and disease. We are pursuing work on these risk factors in a project linked to the Commission on Social Determinants of Health. Such additional approaches to TB control are necessary to significantly curb the epidemic and will contribute to reaching the 2015 Millennium Development Goal related to TB control. Preventing smoking or encouraging people to quit can substantially reduce both the incidence of clinical tuberculosis and tuberculosis deaths. (3) At the same time, it is crucial to strengthen the role of health professionals in tobacco control as promoted in Articles 12 and 14 of the WHO Framework Convention on Tobacco Control. (4) Physicians and public health workers should energetically apply anti-smoking interventions in populations with high levels of subclinical tuberculosis infection. Since exposure to environmental tobacco smoke at home or at work is also a risk for those with compromised respiratory systems, including TB patients, it is crucial to effectively implement the WHO Framework Convention's Article 8 on protection from exposure to tobacco smoke.
Since 2005, WHO has been exploring collaborative activities between TB control and tobacco control efforts. As a first step, the effects of smoking (active smoking and exposure to tobacco smoke) on TB were investigated in a systematic review of the literature jointly undertaken by WHO and the International Union Against Tuberculosis and Lung Diseases. The specific effects studied included those on TB infection and disease, recurrent TB, TB characteristics and case management (delay in seeking care, default, smear conversion, disease severity, acquired drug resistance) and mortality during and after TB treatment.
On the basis of strict and standardized criteria, 42 articles containing 50 studies for data extraction were selected for final inclusion in the meta-analysis. The meta-analysis showed that smoking and exposure to tobacco smoke have a significant impact on susceptibility to TB infection, progression to TB disease and treatment outcomes. The evidence was rated as strong for an association between exposure to tobacco smoke and TB disease, moderate for the association between tobacco use and recurrent TB disease, limited for the association between exposure to tobacco smoke and TB infection, and between tobacco use and TB mortality (both for TB mortality and for TB and death during and after treatment). Limited data supported an association between tobacco use and patient delay in seeking care, default, slower smear conversion and greater severity of disease or drug-resistant …