[Fish intake and the risk of prostate cancer in Japan: a prospective cohort study].
OBJECTIVE
Fish intake may reduce the risk of prostate cancer. However, the results of previous prospective cohort studies have been inconsistent, and almost all have been undertaken in Western countries, where total fish intake is low. We therefore investigated the association between fish intake and the risk of prostate cancer in a prospective cohort study in Japan.


METHODS
We delivered a self-administered questionnaire including items on dietary intake (40-item food frequency questionnaire [FFQ]), and various lifestyle habits, between October and December 1994 to all male National Health Insurance (NHI) beneficiaries aged 40-79 years in Japan. Usable questionnaires were returned from 24,895 (94%) of the participants. We divided the participants into quartiles based on their self-reported fish intake. We used the Cox proportional hazards model to estimate the hazard ratio (HR) and 95% confidence interval (CI) of prostate cancer incidence according to fish intake, after adjustment for potential confounders.


RESULTS
We identified 95 prostate cancer cases during 7 years of follow-up, to the end of December 2001. An inverse association was observed between fish intake and the risk of prostate cancer. The multivariate HRs (95% CI) of prostate cancer across increasing quartiles of fish intake were 1.00, 0.92 (0.48-1.76), 0.73 (0.42-1.28), and 0.72 (0.40-1.33) (P for trend = 0.23). Among participants aged 40-69 years, the multivariate HRs (95% CI) of prostate cancer across increasing quartiles of fish intake were 1.00, 1.26 (0.51-3.11), 0.86 (0.38-1.94), and 1.01 (0.43-2.34) (P for trend = 0.83). On the other hand, among participants aged 70 years or older, the corresponding multivariate HRs (95% CI) were 1.00, 0.63 (0.23-1.69), 0.60 (0.27-1.30), and 0.44 (0.18-1.11) (P for trend = 0.08).


CONCLUSIONS
The risk of prostate cancer tended to decrease among those aged 70 years or older although it was not significant. The relation was not seen in those aged 40-69 years old.
Sato
Fumi
F
Division of Epidemiology, Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan.
Shimazu
Taichi
T
Kuriyama
Shinichi
S
Ohmori
Kaori
K
Nakaya
Naoki
N
Tsuji
Ichiro
I
Arai
Yoichi
Y
D000328:Adult; D000367:Age Factors; D000368:Aged; D000818:Animals; D015331:Cohort Studies; D004032:Diet; D005399:Fishes; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000453:epidemiology* / Q000517:prevention & control*; D012306:Risk; D011795:Surveys and Questionnaires; D013997:Time Factors