Background. Parity and long term use of oral contraceptives have been associated consistently with a decreased risk of ovarian cancer. However, previous reports of the relationship of other reproductive factors (time since first use or last use of oral contraceptives, age at menarche or menopause, age at first birth) with overian cancer have been inconsistent. Methods. The authors studied these relationships in the Nurses' Health Study, a prospective cohort study of 121,700 female registered nurses aged 30–55 years in 1976 when the study began. From 1976 to 1988, 260 cases of confirmed epithelial overaian cancer occurred among 1.2 million person‐years of follow‐up. Results. A Statistically significant inverse association was observed between parity and overian cancer risk (relative risk [RR] = 0.84; 95% confidence interval [CI]=0.77–0.91 per pregnancy); age at first birth was not associated independently with risk. In age‐adjusted analyses, a significant inverse association was noted between long term use of oral contraceptives and ovarian cancer, which was no longer significant after controlling for other ovarian cancer risk factors (RR with ≥5 years' use: 0.65; 95% CI = 0.40–1.05). After control for duration of use, a weak nonsignificant inverse associated was observed with time since first oral contraceptive use and no independent effect of time since last use. Neither age at menarche nor age at menopause use associated significantly with ovarian cancer risk. Conclusions. In this large prospective study, parity was the only reproductive factor that had a substantial independent associated with ovarian cancer. Long term oral contraceptive use also appeared to have an inverse relationship with ovarian cancer, although this association was of borderline significance (P = 0.11) after adjustment for other risk factors. Cancer 1995; 76:284–90.
|Number of pages||7|
|State||Published - Jul 15 1995|
- oral contraceptive use
- ovarian cancer
- reproductive factors