Tobacco and Public Health - TCSC Indonesia

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TOBACCO USE AND RISK OF ORAL CANCER
Prospective follow-up studies
A prospective follow-up study is conducted based on the presence or absence of
exposure of investigation without the information regarding disease status. Therefore,
a follow-up study is less prone to selection bias at the start of the study. However, the
losses to follow-up may still pose an issue for the interpretation of the study results,
especially for diseases, such as cancers, which have long induction and latency periods.
Hammond and Seidman (1980) reported a prospective mortality study of over one
million Americans in 1721 counties in 25 states in the US. The study reported that,
among men, oral cancer mortality rates were 2.3/100 000 for those who never smoked
regularly, 11.7/100000 for pipe and cigar smokers, and 15.0/100 000 for cigarette
smokers. Among women, the oral cancer mortality rates were 2.0/100 000 for those
who never smoked regularly and 6.5/100 000 for cigarette smokers.
Another prospective cohort mortality study from Japan by Akiba and Hirayama
(1990) examined the site-specific cancer risk associated with cigarette smoking, using
the data from 265 000 residents of 29 public health districts in six prefectures throughout
Japan. The study reported a statistically significant dose–response relationship
between cigarette smoking and mortality rate for cancer of the oral cavity, larynx,
esophagus, bladder, and stomach in men. Compared to never smokers, the RRs were 2.5
(95% CI 1.3–5.7) for cancer of the oral cavity and 23.8 (95% CI 5.3–420.0) for cancer
of the larynx among males. Very few women smoked cigarettes in this population.
Chyou et al. (1995) reported a cohort study of upper aerodigestive tract cancer
among 7995 Japanese–American men in Hawaii in which they examined the potential
impact of smoking and other risk factors on the incidence of upper aerodigestive
tract cancer (30 men with oral/pharyngeal cancer, 27 men with laryngeal cancer, and
35 men with esophageal cancer). The study found that current cigarette smokers at
time of examination had a threefold risk for upper aerodigestive tract cancer compared
with never-smokers (RR = 3.2, 95% CI 1.7–5.9). A significant positive linear trend in
relative risk was observed in number of cigarettes smoked per day (Ptrend = 0.002), and
number of years of smoking (Ptrend = 0.0006).
Pipe and cigar smoking
Another major source of exposure to tobacco is through cigar and pipe smoking.
Similar to the observations for cigarettes smoking and oral cancer risk, the vast majority
of studies have identified a strong association between cigar and pipe smoking and oral
cancer risk (Blot et al. 1988; Spitz et al. 1988; Franco et al. 1989; Merletti et al. 1989;
Franceschi et al. 1990; La Vecchia et al. 1990, 1998; Zheng et al. 1990; Mashberg et al.
1993; Schildt et al. 1998; Hayes et al. 1999; Schlecht et al. 1999; Shapiro et al. 2000;
Garrote et al. 2001). With only a few studies, such as the study by Marshall et al. (1992),
reporting little or no association. In some studies, the risk of oral cancer was actually
found to be higher for pipe and cigar smokers than for cigarette smokers.