1. Proving the Links between
Smoking and Lung Disease
Epidemiological and Experimental
Evidence
ALBIO9700/2006JK

2. Epidemiological Evidence
 Epidemiology: the study of patterns of disease
in populations and the factors that influence the
spread of disease
 Epidemiologist discovered a correlation between
lung cancer and cigarette smoking
Number of cigarettes Annual death rate per
smoked per day 100 000 men
0 10
1-14 78
15-24 127
>25 251
Results of study carried out on male doctors in Britain ALBIO9700/2006JK

3.  General:
 Up to 50% of smokers may die of smoking-related
disease
 Tobacco smoking is currently responsible for ~30%
of all cancer deaths in developed countries
 Estimated to account for ~4–5 million deaths a year
worldwide
 Projected to increase to ~10 million a year by 2030.
Thus, if current smoking patterns continue, there will
be >1 billion deaths attributable to tobacco smoking
in the 21st century compared with ~100 million
deaths in the 20th century
ALBIO9700/2006JK

4.  The only other causes of disease with such rapidly
increasing impact are those associated with HIV
infection and, perhaps, obesity in Western countries
 Smokers are 3 times more likely to die in middle age
than are non-smokers
ALBIO9700/2006JK

5.  Chronic obstructive pulmonary
disease:
 Rare in non-smokers
 90% of deaths from chronic obstructive
pulmonary disease are attributed to smoking
 98% of people with emphysema are smokers
 20% of smokers suffer from emphysema
 Deaths from pneumonia and influenza are
twice as high among smokers
ALBIO9700/2006JK

6.  Lung cancer:
 Smokers are 18 times more likely to develop
lung cancer than non-smokers
 1/3 of all cancer deaths are a direct result of
cigarette smoking
 25% of smokers die of lung cancer
 Risk increase if smokers inhale; start young;
increase the number of cigarettes smoked per
day; use high tar cigarettes; smoke for a long
time
ALBIO9700/2006JK

7.  Conclusions drawn from epidemiological data
could be criticised because they only show that
there is an association between the two, not a
causal link between them
 With smoking, it is possible to show direct link
with lung cancer because smoking is the
common factor in almost all cases (Royal College
of Physicians – 1962, 1971, 1977, 1983 and
1992)
 Cigarette smoking is linked with other cancers
ALBIO9700/2006JK

8. Experimental Evidence
 2 lines of evidence:
 Tumours similar to those found in humans
develop in animals exposed to cigarette
smoke
 Beagles used in experiments to investigate the
effect of cigarette smoke on the lungs in the 1960s
 Carcinogens have been identified in tar
 Chemicals extracted and analysed (benzyprene)
 Cancerous growth on painted skin of mice
ALBIO9700/2006JK

9. ALBIO9700/2006JK