Coffee and tea drinking and ovarian cancer risk: Results from the Netherlands cohort study.

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It has been suggested that coffee and tea or its components are related to cancer risk. Several case-control studies and a few cohort studies have been conducted on the association of coffee or tea consumption and the risk of ovarian cancer. Results have been inconclusive however. In 1986, the Netherlands Cohort Study on Diet and Cancer was initiated. A self-administered questionnaire on diet and other risk factors for cancer was completed by 62,573 postmenopausal women. Data were processed and analyzed using the case-cohort approach, enumerating the cases for the entire cohort, and estimating the person years at risk in the cohort using a subcohort. This subcohort was randomly sampled from the entire cohort immediately after the baseline measurement and is being followed up biennially for vital status. Cohort members who reported ovariectomy at baseline or who reported inconsistent or incomplete dietary information were excluded from analysis. Follow-up for cancer was established by annual record linkages with the Netherlands Cancer Registry and the nationwide pathology registry. After 11.3 years of follow-up, data regarding 244 incident epithelial ovarian cancer cases and of 2,136 subcohort members were available for analysis. Rate ratios (RRs) were estimated using the Cox proportional hazards model. Multivariate RRs were adjusted for age at baseline, use of oral contraceptives, parity, use of postmenopausal hormones and cigarette smoking. In analysis of coffee drinking, correction was made for tea drinking and vice versa. More than 96% of the subcohort members reported drinking coffee and more than 89% reported drinking tea. Mean daily consumption of coffee and tea was 4.0 cups (SD, 2.0) and 3.1 cups (SD, 2.1) per day, respectively, for subcohort members. In multivariate analysis and compared to women with a coffee consumption of 1-<3 cups/day, the RRs of ovarian cancer for women with coffee consumption of 0-<1, 3-<5 and >=5 cups/day were 0.53, 1.16 and 1.33, respectively (95% confidence interval (CI) for the top category, 0.89-2.00; p for trend, 0.02). The risk of ovarian cancer increased with 9% per cup of coffee per day (95% CI, 2-17%). Compared to women with a tea consumption of 1-<3 cups/day, the RRs of ovarian cancer for women with tea consumption of 0-<1, 3-<5 and >=5 cups/day were 0.97, 1.05 and 0.54, respectively (95% CI for the top category, 0.31-0.94; p for trend, 0.20). These data support a positive association between coffee consumption and ovarian cancer in this population and an inverse association for tea consumption.