Monaldi Arch Chest Dis
2008; 69: 2, 83-85
Tobacco and tuberculosis
Human beings are not all equally sensitive to
infection with M. tuberculosis if exposed to a
source of contamination. Among persons exposed
to the contact with an index case with transmissi-
ble tuberculosis, some will develop a latent infec-
tion. Of those with a latent tuberculosis infection,
some will develop a clinical tuberculosis, and
among those suffering from tuberculosis some will
die. Several individual factors modulate these
risks. Many of them, like HIV infection, steroid
treatment or diabetes, are related to the immune
defence mechanisms. Smoking, as one of the most
potent irritants to the airways, also influences the
local immune mechanisms of defence against in-
fection and has long been suspected of influencing
the development and outcome of tuberculosis, but
the evidence were anecdotal . Other factors, fre-
quently associated with tuberculosis and with
smoking, like abuse of alcohol, social deprivation,
homelessness and unemployment were suspected
to confound the relation [2, 3]. Recently, two sys-
tematic reviews of the existing literature have ad-
dressed in details the possible influence of smok-
ing on several aspects of tuberculosis and have
come to remarkably similar conclusions [4, 5]. Si-
multaneously, The International Union against TB
and Lung Disease and the WHO have prepared
documents addressing the relations between tobac-
co and tuberculosis, and a plan for further action
The mechanisms by which tobacco smoke can
influence the mucosal defences responsible for the
control of mycobacterial infection include the in-
crease of the production of bronchial secretions,
the decrease in mucociliary clearance, and the im-
pairment of macrophage function. This leads to a
decrease of bacterial adherence at the surface of
macrophages, a decrease of their phagocytic abili-
ty, a decrease of the release of proinflammatory
cytokines with impaired intracellular killing ca-
pacity and a reduced production of TNF-a and ni-
tric oxide (summary in ).
The influence of tobacco smoke on tuberculo-
sis can be assessed for different types of risk:
a) risk of infection if exposed to tuberculosis
(children exposed to passive smoking and
b) risk of disease if infected, (adults and chil-
c) risk of death from tuberculosis.
Risk of infection (if exposed)
Smokers have an increase in the risk of infec-
tion (usually assessed by the size of the tuberculin
reaction) if exposed to tuberculosis. This increase
has been observed in adult smokers, as well as in
non-smoking adults and children passively ex-
posed to tobacco smoke. The risk for children pas-
sively exposed to tobacco smoke and tuberculosis
was assessed in several studies in US , India
, South Africa  and Spain . The rela-
tive risk was proportional to the intensity and du-
ration of exposure and is evaluated between 1.7
and 3.2. The increased risk of infection for active
smokers was demonstrated in UK among elderly
nursing home residents , in adults in South
Africa , and Vietnam  and in incarcerated
adults in Pakistan . The risk is also proportion-
al to the intensity and duration of smoking. The
OR lies between 1.72 and 3.2 .
Risk of disease (if infected)
Once infected, only a minority of patients will
develop tuberculosis, estimates being between
10% for adults and 50% for infants under the age
of 1 year . Individual factors influence this
rate, the most important being immune deficiency
due to HIV, immunosuppressive therapy or dia-
Keywords: Tobacco smoke, Tuberculosis, Infection, Passive smoking, Developing countries.
Department of ambulatory care and community medicine, University of Lausanne, Switzerland.
Correspondence: Jean-Pierre Zellweger, MD, Department of ambulatory care and community medicine, University of Lausanne,
Switzerland; e-mail: email@example.com
ABSTRACT: Tobacco and tuberculosis. J.P. Zellweger.
Smoking is not only the most important source of avoid-
able disability and death, but a risk factor for TB infection,
disease and death. Even passive smoking exposure may in-
crease the risk of infection and disease in adults and children
exposed to TB. Considering the increase in tobacco con-
sumption in developing countries, where the prevalence of
TB is the highest, smoking may be responsible for a large
part of the burden of disease. Therefore, medical advice and
counselling in smoking cessation is an important activity for
all care providers engaged in management of TB.
Monaldi Arch Chest Dis 2008; 69: 2, 83-85.
betes. The increase in risk for smokers compared
to non smokers is evaluated up to 4.6 for the de-
velopment of disease. Furthermore, passive smok-
ing exposure also increases the risk of developing
tuberculosis if infected, particularly among chil-
dren, where the relative risk is between 5 and 9.3
One of the reviews also addressed the relation
between exposure to indoor air pollution (mainly
wood smoke from cooking, a general problem in
many developing countries) and demonstrated that
this was also associated with a higher risk of TB
Death from tuberculosis
Once tuberculosis has developed, most pa-
tients will be cured by an adequate treatment but in
some settings the death rate may still be elevated.
This is particularly the case among elderly patients
with diverse comorbidities, patients with lung de-
struction and chronic obstructive pulmonary dis-
eases. The OR for death from tuberculosis associ-
ated with active smoking is estimated to be 2.2 .
In India, a large survey has concluded that up to
half of all TB deaths can be attributed to smoking
. These date were confirmed by a prospective
Some studies have also concluded that the
severity of disease, the speed of bacteriological
conversion and the rate of failure and relapse may
be negatively influenced by smoking .
Public Health impact of smoking
among TB patients
Smoking has a large impact on public health,
due to the increase in risk of several severe and po-
tentially lethal diseases. It appears therefore that
the increase in smoking habit is not only the cause
of an increase in the prevalence of COPD [23, 24]
but also of tuberculosis. Considering the large and
increasing number of smokers in many developing
countries which also experience a high burden of
tuberculosis, the population attributable risk is
now considered to be significant . A recent
evaluation by WHO has come to the conclusions
that up to 16% of cases of tuberculosis in low-in-
come countries and 28% in high-burden countries
could be attributed to smoking . The associa-
tion between smoking and tuberculosis may be
even higher in populations with a large proportion
of HIV infection .
One of the intriguing questions is to know why
it has taken so long to realize the interaction be-
tween smoking and tuberculosis. One of the rea-
sons may be the fact that smoking was considered
a health problem mainly in developed countries
with a low burden of tuberculosis, whereas devel-
oping countries with a high burden of tuberculosis
had until recently a low or moderate prevalence of
smoking. One notable exception is Eastern Europe,
where the prevalence of both smoking and tubercu-
losis is high. Considering the increase in smoking
habits of the countries with the highest burden of
TB, this interaction can no more be ignored.
The practical consequence for all health care
workers active in the management of tuberculosis
is the clear obligation to address the problem of
smoking with all patients under treatment for tu-
berculosis and to advise the smokers to stop smok-
ing. In order to achieve this, training of health care
workers has to be provided. A study has demon-
strated the impact of minimal advice in such set-
tings . Patients treated by trained health care
workers have a greater chance of stopping smok-
ing at the end of the treatment of tuberculosis than
patients treated by untrained health care profes-
sionals. Tobacco cessation has to be included in
standard practice for all caregivers engaged in the
management of tuberculosis .
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Fig. 1. - Impact of smoking on the airways (after ref 8).Fig. 2. - Interactions between smoking and tuberculosis.
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