Ovarian Cancer and Body Size: Individual Participant Meta-Analysis Including 25,157 Women with Ovarian Cancer from 47 Epidemiological Studies Collaborative Group on Epidemiological Studies of Ovarian Cancer*

Background: Only about half the studies that have collected information on the relevance of women’s height and body mass index to their risk of developing ovarian cancer have published their results, and findings are inconsistent. Here, we bring together the worldwide evidence, published and unpublished, and describe these relationships. Methods and Findings: Individual data on 25,157 women with ovarian cancer and 81,311 women without ovarian cancer from 47 epidemiological studies were collected, checked, and analysed centrally. Adjusted relative risks of ovarian cancer were calculated, by height and by body mass index. Ovarian cancer risk increased significantly with height and with body mass index, except in studies using hospital controls. For other study designs, the relative risk of ovarian cancer per 5 cm increase in height was 1.07 (95% confidence interval [CI], 1.05–1.09; p,0.001); this relationship did not vary significantly by women’s age, year of birth, education, age at menarche, parity, menopausal status, smoking, alcohol consumption, having had a hysterectomy, having first degree relatives with ovarian or breast cancer, use of oral contraceptives, or use of menopausal hormone therapy. For body mass index, there was significant heterogeneity (p,0.001) in the findings between ever-users and never-users of menopausal hormone therapy, but not by the 11 other factors listed above. The relative risk for ovarian cancer per 5 kg/m increase in body mass index was 1.10 (95% CI, 1.07–1.13; p,0.001) in never-users and 0.95 (95% CI, 0.92–0.99; p = 0.02) in ever-users of hormone therapy. Conclusions: Ovarian cancer is associated with height and, among never-users of hormone therapy, with body mass index. In high-income countries, both height and body mass index have been increasing in birth cohorts now developing the disease. If all other relevant factors had remained constant, then these increases in height and weight would be associated with a 3% increase in ovarian cancer incidence per decade. Please see later in the article for the Editors’ Summary. Citation: Collaborative Group on Epidemiological Studies of Ovarian Cancer (2012) Ovarian Cancer and Body Size: Individual Participant Meta-Analysis Including 25,157 Women with Ovarian Cancer from 47 Epidemiological Studies. PLoS Med 9(4): e1001200. doi:10.1371/journal.pmed.1001200 Academic Editor: Eduardo L. Franco, McGill University, Canada Received July 15, 2011; Accepted February 24, 2012; Published April 3, 2012 Copyright: 2012 Collaborative Group on Epidemiological Studies of Ovarian Cancer. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: Funding for this collaborative reanalyis of original data was provided by Cancer Research UK. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Abbreviations: CI, confidence interval; g-s CI, group-specific confidence interval * E-mail: [email protected] PLoS Medicine | www.plosmedicine.org 1 April 2012 | Volume 9 | Issue 4 | e1001200