Tobacco causes a wide spectrum of fatal and nonfatal
diseases. Although tobacco is smoked and used in a wide variety of ways all over the world, especially in India,
the epidemiologic evidence of specific harmful effects of
tobacco is based largely on studies of people who smoke
cigarettes, the most popular form in the West. However,
studies on some of the effects of cigars, pipes, bidi and
smokeless tobacco show that all forms of tobacco use
are harmful. We discuss here several potentially fatal
diseases implicating tobacco, as found in studies of ciga-
rette smokers and people exposed to second-hand smoke.
A few health risks to tobacco workers are mentioned. A
discussion of tobacco-related disease in cigar and bidi
smokers and smokeless tobacco consumers is given below.
Tobacco and cancer
The role of tobacco in increasing the risk of lung cancer is
widely known. Richard Doll’s 1950 paper, demonstrating
the association between smoking and lung cancer, has
become a public health classic
4
. Many people may not
realize that tobacco use increases the risk of cancer at
many sites in the body: the head and neck (covering
cancers of the oesophagus, larynx, tongue, salivary glands,
lip, mouth, and pharynx), urinary bladder and kidneys,
breast, uterine cervix, pancreas, colon and other sites
5
.
Lung cancer
How much risk of lung cancer does cigarette smoking
pose? On an average, smokers increase their risk of lung
cancer between 5 and 10-fold, and in developed coun-
tries, smoking is responsible for more than 80% of all
lung cancers. Using American data, 24% of men who
smoke can expect to develop cancer during their lifetime.
Recently, the spread of tobacco use to developing coun-
tries has led to similar disease patterns there. In a report
from India, roughly two-thirds of all patients with lung
cancer were smokers of either cigarettes and/or bidis
(hand-rolled tobacco in tendu leaves). Among 54 female
patients, only 5% were smokers, reflecting both the low
prevalence of tobacco use among women and the cancer-
causing effects of environmental tobacco smoke
6
. In a
study of 1,000,000 deaths in China, lung cancer risk was
found to be two to four times higher among men who
smoked compared to nonsmokers and this association was
generally consistent over both rural and urban areas
7
.
Lung cancer remains a disease of dismal prognosis.
Although one-year all-stage survival is reported to have
increased from 32% in 1973 to 41% in 1994, five-year
survival has remained unchanged at 14%. Early detection
has been promoted as a potentially valuable intervention
but its cost-effectiveness puts it beyond the reach of all
but the best funded health care systems, and even
then, early detection pales in comparison to the cost-
effectiveness of comprehensive programmes and policies
to reduce tobacco consumption.
Head and neck cancer
Tobacco use has long been linked to head and neck
cancers, particularly in tissues through which inhaled
smoke passes. For oral cancers, men who smoke have a
27-times higher rate of oral cancer than men who do not
smoke. For laryngeal cancer, rates are 12 times higher
among smokers.
Urinary bladder and kidney cancer
In the Western countries, tobacco use is the single most
important cause of bladder cancer, accounting for an
estimated 40–70% of all cases. Smokers’ risk of bladder
cancer is 2–3 times higher than of nonsmokers. Poly-
aromatic hydrocarbons contained in cigarette smoke are
known carcinogens and may be absorbed into the blood
and transported to the bladder where the cells are unable
to withstand their carcinogenic effects.
Breast cancer
For women in developed countries, cases of breast cancer
have been rising over the last few decades, in consonance
with the rapid increase in female smoking that has occurred
from the middle of the 20th century. Data on links between
breast cancer and smoking have, however, been mixed,
and this has led to conflicting health messages. In Danish
women interviewed at the time of mammography, smoking
for more than 30 years was associated with a 60% higher
risk of breast cancer and an age of onset at an average of
eight years earlier, when compared with nonsmokers.
Given that breast cancer incidence is soon to be
eclipsed by lung cancer incidence among women, further
data clarifying the role of smoking in causing breast
cancer should be of value in strengthening efforts to
inform and assist women to quit smoking.
Uterine cervix cancer
The effect of tabacco on cervical cancer has only been
recently recognized, in part because women who smoke
may also have other risk factors for cervical cancer,
particularly exposure to human papilloma virus. Never-
theless, there is now general consensus that cigarette
smoking increases risks of cervical cancer, particularly
among women smoking as many as 40 cigarettes daily,
and is responsible for approximately 30% of cervical
cancer deaths in the US.
Pancreatic cancer
Smoking is estimated to be responsible for 30% of
pancreatic cancer. Like for bladder cancer, carcinogens
inhaled by the smoker are thought to enter the blood
stream and reach the pancreas via the blood and the bile, secreted by the liver to aid digestion. Pancreatic cancer
prognosis remains very poor, with 5-year survival less
than 5% in most reports.
Colon cancer
Colon cancer risk is also greater among smokers, pre-
sumably due to the transport of carcinogens to the colon
from inhaled or swallowed tobacco smoke. Data support-
ing this association come from several longitudinal
studies in which groups of people are followed over many
years to record the occurrence of various illnesses.
Based on data from both male and female health pro-
fessionals in the US, smoking appears to double the risk
of colon cancers. Most colon cancers begin as polyps.
Risk of cancer increases with polyp size and there is
a dose–response relationship with increasing years of
tobacco use associated with larger polyps and, after 35
years of smoking, colon cancer.
Tobacco and atherosclerotic diseases
In atherosclerosis, blood vessels are narrowed as plaques
of lipid material build up in them, typically when ravaged
by harmful substances (e.g. free radicals – molecules with
unpaired electrons, that grab electrons from other sub-
stances around them, damaging them) contained in high
concentrations in tobacco ‘tar’. Atherosclerosis reduces
blood flow through the coronary arteries supplying the
heart muscle, the carotid arteries feeding the brain and
the small vessels in the legs. Smoking can increase the
size of plaques in the carotid arteries by over three-fold,
as demonstrated by studies of identical twin pairs, in
which one smokes and the other does not, thus cancelling
out the effects of genetic predispositions to atherosclero-
sis
8
. The implication of smoking in heart disease, stroke
and peripheral vascular disease is discussed below.
Heart disease
A heart attack (myocardial infarction) occurs when a dis-
eased coronary artery is blocked by a blood clot or a
breakup of the plaque material. The link between smoking
and heart (cardiovascular) disease has been well described
in populations all over the world. Twenty-five years of
follow-up in the Seven Countries Study (16 cohorts of
men, aged 40 to 59 at enrolment in the USA, Finland, the
Netherlands, Italy, Croatia, Serbia, Greece and Japan)
reported a dose-dependent increase in the risk of death.
After 25 years, 57.7% of persons smoking 30 cigarettes
per day had died, compared to only 36.3% of non-
smokers
9
. Additional long-term data come from a 40-year
follow up of British physicians noted that excess mortality
from cardiovascular disease was twice that among smo-
kers compared to non-smokers but this ratio was even
more extreme during middle age
10
.
The data for men and women differ slightly, but recent
work underlines the importance of smoking as a cause of
heart attack in both. In a Norwegian study, rates of myo-
cardial infarction among women who smoked were six
times higher than in female non-smokers and rates among
men, three times higher than among male nonsmokers
11
.
Danish investigators concluded that women might be
more sensitive to tobacco, as risks of heart attack due to
current smoking and total tobacco exposure were consis-
tently higher in women than in men.
In an increasing number of health systems, patients are
offered expensive therapies, like coronary bypass surgery
or angioplasty, to open or bypass vessels that have
become too narrow to supply enough oxygen to the heart.
American data show that after an average of four and a
half years of follow-up of 3437 patients, people who con-
tinued to smoke after angioplasty had a 76% increased
risk of death, compared to nonsmokers, and a 44% higher
risk of death compared to those who quit smoking12
.
Stroke
A stroke occurs when blood flow to the brain is reduced,
often by a blood clot, or less commonly, when a blood
vessel in the brain bursts. Non-fatal strokes often leave
their victims substantially disabled. Research has shown
that tobacco use increases the risk of stroke. Stroke risk is
also increased among people with uncontrolled blood
pressure. Smoking cessation and treatment of hyperten-
sion combined can reduce the risk of stroke and also that
of cardiovascular and peripheral vascular disease.
How high is the risk of stroke from tobacco use?
Research results vary, but data from US physicians show
a 2.71 higher risk of non-fatal stroke among persons
smoking more than 20 cigarettes a day and data from the
UK report a 3.7 times higher risk of stroke among current
smokers. The risk among current smokers may be as high
as seven times greater than that among non-smokers
for subarachnoid haemorrhage (blood between the two
innermost of the three membranes protecting the brain),
which if survived is likely to cause more devastating
disability13
.
The risk of stroke among smokers increases with
the amount smoked so that heavy smokers can make the
greatest improvements to their health by quitting. The
good news is that several studies, with both male and
female subjects, report that five years after quitting, the
former smoker has no higher risk of stroke than the non-
smoker
13
.
Peripheral vascular disease
Peripheral vascular disease refers to a cluster of condi-
tions in which atherosclerosis occurs in the peripheral
circulation, particularly in the legs. Peripheral vascular
disease, unlike myocardial infarction, has a relatively low risk of death but causes substantial disability as affected
limbs are at higher risk of amputation and infection.
The link between peripheral vascular disease and
tobacco use was described in the early 1900s by Buerger
after whom one form of vascular disease, rare in non-
smokers, is named.
Tobacco and diabetes
Diabetes mellitus is a chronic disease affecting multiple
systems in the body and often leading to substantial dis-
ability due to blindness, vascular disease necessitating leg
amputation, kidney failure and premature death. Tobacco
use increases the risk of diabetes, which itself speeds up
atherosclerosis, with its attendant diseases.
There are two forms of diabetes mellitus, insulin-
dependent (IDDM) and non-insulin-dependent (NIDDM).
NIDDM usually is diagnosed in midlife and may be
treated with diet modification, drugs and lifestyle modifi-
cation to encourage regular exercise. Studying the effect
of smoking on NIDDM is complicated by the fact that
people who smoke are more likely to be sedentary and
overweight, therefore already at risk for NIDDM. This
problem has been solved by following a group of non-
diabetic people over time and identifying diabetics when
they are initially diagnosed with NIDDM, so that their
smoking habits at the time of diagnosis and in the years
leading up to diagnosis are recorded.
Male health care professionals in the US who smoke 25
or more cigarettes daily appear to have a double risk of
NIDDM14
. This is important because once diagnosed, NIDDM
is often more severe in those who continue to smoke.
Tobacco and chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease (COPD) encom-
passes chronic bronchitis and emphysema. Chronic bron-
chitis refers to a productive cough for at least three
months in each of two successive years for which other
causes have been ruled out. Emphysema involves destruc-
tion of the lung architecture with enlargement of the
airspaces and loss of alveolar surface area.
COPD prevalence increases with age, but there is a
dramatic synergy with smoking. Unlike heart disease,
quitting smoking does not produce substantial reversal of
tobacco’s harmful effects once COPD is established. As a
result, in many developed countries, COPD is increasing
as a cause of death as cardiovascular death rates fall
5
. As
with other tobacco-associated adverse health effects,
smoking either cigarettes or cigars increases risks of
COPD. Thus, cigar smokers are reported to have a 45%
higher risk of COPD when compared to nonsmokers
15
.
Tobacco and osteoporosis
As populations age the world over, osteoporosis, or loss
of bone mineral density, will generate an increasing bur-
den of disease. Far more common among women than
men, osteoporosis itself is less a disease than a risk factor
because people with osteoporosis have much higher risk
of fractures, particularly of the hip and vertebrae.
Hip fractures often cause substantial disability and may
prevent someone from returning home even after surgery
and rehabilitation, if their home is unsuitable for their
impaired mobility. In even the most resource-rich health
care systems, the resources that will be consumed by
treatment and care of persons with such fractures is
expected to grow exponentially.
The strongest evidence of the effects of smoking in
decreasing bone mineral density comes from a meta-
analysis which considered 29 studies and concluded that
roughly one in eight hip fractures is attributable to ciga-
rette smoking. Hip fracture risk among smokers is greater
at all ages but rises from 17% greater at age 60 to 71% at
age 80 and 108% at age 90 (ref. 16). Risks are lower in
former smokers, suggesting a benefit of quitting smoking
in slowing the rate of bone loss.
Tobacco and the thyroid
The thyroid gland sits in the neck and is responsible for
metabolic control. It produces thyroid hormone, which is
involved in many of the body’s metabolic processes.
Among women with hypothyroidism (insufficient thyroid
hormone), smoking is reported to be responsible for both
decreasing secretion of thyroid hormone and blocking its
action, thus exacerbating the symptoms of hypothyroidism
and reducing basal metabolism17
. Symptoms include obe-
sity, poor appetite, fatigue, poor memory, slow heart beat,
low body temperature, cold intolerance, reduced sweating,
dry, rough skin, constipation, joint pain and muscle
cramps. Case-control studies have reported that smoking
is over seven times more frequent among hypothyroid
patients with Graves’ opthalmopathy, a severe form of
hypothyroidism involving the eyes.
Tobacco and women’s health
The adverse health effects of tabacco are universal in that
they increase risks of cancer and heart disease among all
smokers and quitting smoking reduces these risks. How-
ever, for women, smoking carries special risks. In addi-
tion to cancer risks unique to women and a greater risk for
osteoporosis, smoking by pregnant women and mothers
may affect their offspring. Pregnancy outcomes, including
lower birth weight and intrauterine growth retardation, are
more frequent among women who smoke than among
those who do not smoke. Smoking during pregnancy is also
a major cause of sudden infant death syndrome (SIDS) and
decreased lung function, which are well-documented
effects
. In India a high proportion of women use smokeless
tobacco even during their pregnancy. This has been shown
to cause a range of adverse reproductive outcomes