Tobacco and Public Health - TCSC Indonesia

450
CIGARETTE SMOKING AND COLORECTAL CANCER
exhibited only weak evidence of an increased risk (not statistically significant;
RR = 1.44). This study had a follow-up of 40 years, but did not present time-lagged
analyses. In a population-based case–control study of 174 colorectal cancer cases in
Great Britain (Welfare et al. 1997), male and female smokers were at increased risk
(OR = 1.77; 95% CI = 1.03–3.14).
A Norwegian cohort study of 68 825 men and women documented 51 fatal colon
cancers and 40 fatal rectal cancers from 1972–88 (Tverdal et al. 1993). Males who had
smoked in the past had a moderately increased risk for fatal colon cancer (RR = 1.2)
and fatal rectal cancer (RR = 1.4), and male current smokers, but not female smokers,
were at elevated risk from fatal colon cancer (RR = 1.5) and rectal cancer (RR = 1.8).
In a cohort study in Finland (Knekt et al. 1998), 56 973 men and women were
followed from 1966–72 to 1994. A non-statistically significant overall association was
observed, but for follow-up periods of between 11 and 20 years, a significant increased
risk was observed for smokers (RR = 1.57; 95% CI = 1.09–2.24). At baseline, smokers
had smoked for 20 years on average. This association was limited to men (RR = 1.94;
95% CI = 1.25–2.24), who smoked more than women. In a comparison of colorectal
cancer risk for persons recorded as smokers in both of two baseline examinations,
a significant increase in risk was observed in the consistent smokers (RR = 1.71; 95%
CI = 1.09–2.68).
An Icelandic cohort study documented 145 colorectal cancers in 11 580 women and
193 cases in 11 366 men followed from 1968 to 1995 (Tulinius et al. 1997). In this
cohort, the prevalence of current smoking at baseline was higher in women than in
men (1–14 cigarettes/day: 11% of men, 20% of women; 15–24 cigarettes/day: 13% of
men, 16% of women; 25+ cigarettes/day: 6% of men, 3% of women). Among women,
risk of colorectal cancer increased with increasing level of cigarette smoking (multivariate
RRs = 1.37, 1.53, 2.48). Results were not presented for men (Tulinius et al. 1997).
In a Yugoslavian hospital-based case–control study over 1984–86 (Jarebinski et al.
1988, 1989), risk of colorectal cancer was not elevated among men and women
who had smoked for 1–30 years (RR = 1.0), but risk was elevated for total colorectal
(RR = 2.0) and rectal cancer (RR = 2.7) among long-term smokers (30+ years).
The largest study non-supportive of a relationship between smoking and colorectal
cancer risk was a hospital case–control study of 955 cases of colon cancer and 629 cases
of rectal cancer in northern Italy (D’Avanzo et al. 1995). Cancers of the colon and
rectum were not associated with number of cigarettes smoked, number of pack-years,
duration, time since initiation, and time since quitting.
Several studies of smoking and colorectal cancer risk were conducted in Sweden,
producing mixed results. A random sample of 26 000 Swedish women were asked
about their smoking status in the early 1960s and then were followed for 26 years
(Nordlund et al. 1997). No significant association was observed, except for a
slight increase in smokers of 16+ cigarettes per day at baseline (RR = 1.42; 95%
CI = 0.77–2.60). However, this study was conducted before 1990. A case–control study