Tobacco and Public Health - TCSC Indonesia

TONGZHANG ZHENG ET AL. 415
per day (P trend < 0.001). An alcohol-adjusted OR of 14.8 (95% CI 3.1–70.4) was
observed for those who smoked 25 or more cigarettes per day.
In a combined analysis of two hospital-based case–control studies from Italy and
Switzerland involving 1280 oral and pharyngeal cases and 4179 controls, La Vecchia et al.
(1999) reported an OR of 8.4 (95% CI 6.6–10.6) for current smokers. A significantly
reduced risk was observed following smoking cessation: the ORs were 6.2 for those
who had stopped smoking for less than 2 years, 4.5 for those who had stopped for
3–5 years, 3.5 for those who had stopped for 6–9 years, 1.6 for those who had stopped
for 10–14 years, and 1.4 for those who had stopped for 15 or more years.
Garrote et al. (2001) reported the results from a case–control study of tobacco smoking
and risk of oral and oro-pharyngeal cancers in Cuba. A strong dose–response was
reported between cigarette smoking per day and risk of oral cancer among current
smokers (P trend < 0.01). The alcohol-adjusted OR for smoking 30 cigarettes or more
per day, compared with never smokers, was 20.8 (95% CI 8.9–48.3) among current
smokers. Former smokers also had an OR of 6.3 (95% CI 3.0–13.4), but risk was
significantly reduced after 10 or more years smoking cessation.
Population-based case–control studies
A potential advantage of population-based case–control study design is that controls
are randomly selected from the population which produced the cases, and therefore,
more likely to represent the population with regards to the major risk factors. However,
the relatively higher refusal rate from potential study subjects may still hamper the
interpretation of the study.
In a multicenter study in the four areas of the US, Blot et al. (1988) found that,
compared with never smokers, cigarette smokers had twice the risk in males (OR = 1.9,
95% CI 1.3–2.9), and three times the risk in females (OR = 3.0, 95% CI 2.0–4.5). The
risks of oral cancer rose with the number of cigarettes smoked per day and with the
duration of cigarette smoking. Those who smoked only filter cigarettes had a 50%
(95% CI 30–80) of the risk of those who smoked only non-filter cigarettes, and smoking
cessation resulted in a rapid decline in risk.
In a multi-center case–control study in four European countries, Tuyns et al. (1988)
reported a clear dose–response relationship between cigarette smoking and risk of
cancer of the larynx and hypopharynx. For those who smoked more than 26 cigarettes
per day, the ORs were 24.0 (95% CI 11.8–48.7) for cancer of the supraglottic, 10.2
(95% CI 5.4–19.3) for cancer of the glottic and subglottic, 9.4 (95% CI 3.2–28.0) for
cancer of the epilarynx, and 20.0 (95% CI 7.9–51.0) for cancer of the hypopharynx.
The study also found that earlier age started smoking carried a higher risk. Unlike the
study by Merletti et al. (1989), the smokers of exclusively filter cigarettes in this study
were found to have only half the risk of laryngeal or hypopharynx/epilarynx cancer as
compared with smokers of only plain cigarettes. As reported by Schlecht et al. (1999)
and De Stefan et al. (1998), smokers of black tobacco cigarettes had higher risk than