Cigarette smoking and the risk of ovarian cancer in the Japanese population: findings from the Japanese Collaborate Cohort study.
OBJECTIVE
The many studies into the relation between cigarette smoking and the risk of ovarian cancer have produced inconsistent results. Here we investigated this relation using data from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk, initiated in 1988.


METHODS
A self-administered questionnaire on smoking habits and other risk factors for cancer was completed by 34 639 Japanese women. After 7.6 years of follow up, 39 cases of ovarian cancer were available for analyses. Cox proportional-hazards models were used to compute relative risks (RR) and to adjust for confounders.


RESULTS
Relative to those who had never smoked, the RR of ovarian cancer were 1.63 (95% confidence interval [CI] = 0.21-12.50) for former smokers and 2.27 (95% CI = 0.85-6.08) for current smokers. Among current smokers, the RR were 1.48 (95% CI = 0.20-10.92), 5.56 (95% CI = 1.68-19.06), and 1.86 (95% CI = 0.25-14.30) among women who smoked <10, 10-19, and at least 20 pack-years ([number of cigarettes smoked per day/20] x number of years subject has smoked), respectively, relative to those who had never smoked. A test for trend was statistically significant (P = 0.044).


CONCLUSIONS
These data indicate that cigarette smoking increases the risk of developing ovarian cancer in the Japanese population.
Niwa
Yoshimitsu
Y
Department of Preventive Medicine/Biostatistics and Medical Decision Making, Nagoya University Graduate School of Medicine, Nagoya, Japan. ytt-niwa@xg7.so-net.ne.jp
Wakai
Kenji
K
Suzuki
Sadao
S
Tamakoshi
Koji
K
Lin
Yingsong
Y
Yatsuya
Hiroshi
H
Kondo
Takaaki
T
Nishio
Kazuko
K
Yamamoto
Akio
A
Tokudome
Shinkan
S
Hamajima
Nobuyuki
N
Toyoshima
Hideaki
H
Tamakoshi
Akiko
A
D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007564:Japan; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000453:epidemiology* / Q000209:etiology; D016016:Proportional Hazards Models; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*