Multivariabel Cox proportional hazards regression models for time-varying covariates (also called extended Cox models) were used to estimate relative risks (RRs) and 95% confidence intervals (CIs), stratifying on follow-up time and adjusting for age,BMI,parity,oral contraceptive use, menopausal status/ postmenopausal hormone use, cigarette smoking, physical activity, osteoporosis, and a family history of ovarian cancer (time-varying covariates were age, BMI, use of postmenopausal hormones, and osteoporosis )