Relationship between body mass index and the risk of ovarian cancer in the Japanese population: Findings from the Japanese Collaborate Cohort (JACC) study

Aim: The incidence of ovarian cancer in Japan has increased since the 1970s. The many studies that have assessed the relationship between body mass index (BMI) and the risk of ovarian cancer have produced contradictory results. Here we investigated this relation using data from the Japan Collaborative Cohort Study for the Evaluation of Cancer Risk, which was initiated in 1988. Methods: A self-administered questionnaire on dietary habits and other risk factors for cancer was completed by 36 456 Japanese women. After 7.6 years of follow up, 38 cases of ovarian cancer were available for analysis. Cox proportional-hazards models were used to compute relative risks and to adjust for confounders. Results: Compared to women with BMI of 18.5-24.9 kg/m ², the relative risk of ovarian cancer was 2.24 (95% CI = 1.10-4.21) for BMI of 25.0-29.9 and 1.78 (95% CI = 0.24-13.34) for BMI of ≥30 kg/m ². A test for trend revealed that this finding was statistically significant (P = 0.014). Conclusion: The results of this study suggest that being overweight is independently associated with a higher risk of developing ovarian cancer in the Japanese population.