Tobacco and Public Health - TCSC Indonesia

20
THE GREAT STUDIES OF SMOKING AND DISEASE IN THE TWENTIETH CENTURY
become available for most of the nation until 1930, the age-adjusted lung cancer death
rate increased approximately fivefold from 1930 to the mid-1940s (Thun et al. 2000).
For some years it was debated whether the apparent increase in lung cancer incidence
and death rates represented a true increase in occurrence, or merely an artifact of
improved diagnosis. Skeptics noted that several technologies introduced from the
1920s onwards could have increased recognition of previously undiagnosed disease
(Doll 1998b). These included the widespread introduction of chest X-rays in the
United Kingdom in the 1920s, bronchograms in the 1930s, and bronchoscopy in the
1950s. Open-chest surgery became practicable following improvements in anesthesia
during the Second World War (Doll 1998b). The introduction of sulfapyridine in 1938
reduced mortality from pneumonia that had previously been lethal in the early stages
of lung cancer, allowing cases to live long enough to be diagnosed. Nevertheless, the
continued increase in lung cancer over several decades, and its more frequent diagnosis
in men than women, made it more and more unlikely that improved diagnosis could
explain the entire increase (Doll 1998b).
Five case-control studies published in 1950
In 1950 the publication of five case-control studies reporting an association between
smoking and lung cancer (Doll and Hill 1950; Levin et al. 1950; Mills and Porter 1950;
Schrek et al. 1950; Wynder and Graham 1950) provoked sudden interest among the
medical and scientific communities in the potential health hazards of tobacco use. The
two studies that drew the most attention were the British study by Doll and Hill (1950)
and an American study by Wynder and Graham (1950). These were considerably larger
than were earlier case-control studies of smoking and lung cancer (Muller 1939;
Schairer and Schioninger 1943; Wassink 1948), had higher response rates, and defined
smoking more precisely. The association between smoking and lung cancer was very
strong in the largest case-control studies in Britain [odds ratio (OR) = 14] (Doll and
Hill 1950) and the United States (OR = 6.6) (Wynder and Graham 1950); and even the
study by Schrek et al., which showed the weakest association, had an odds ratio of 1.8
(Schrek et al. 1950).
Although the case-control studies suggested that cigarette smoking was an important
cause of lung cancer, the results were viewed as provocative rather than conclusive.
Scientists were initially uncertain of the utility of case-control studies for studying
chronic conditions such as cancer, since the methods had been developed for infectious
diseases (Doll 1998b). Some epidemiologists questioned whether smokers with
lung cancer were more likely to be hospitalized because of cough, perhaps introducing
selection bias (Berkson 1955), or whether the control group might be biased by cultural
factors related to smoking (Hammond 1953). Cuyler Hammond, of the American
Cancer Society, noted that the studies ‘disagree so markedly in their measurement of the
size of that relationship’ that one could not tell whether the relationship is of ‘major clinical
interest’ or ‘of academic interest only’ (Hammond and Horn 1952). In retrospect,