Person:

Charlton, Brittany

Purpose—The influence of reproductive factors on colorectal cancer, including oral contraceptive (OC) use, has been examined, but less research is available on OC use and adenomas.

Methods—Participants of the Nurses' Health Study who had a lower bowel endoscopy between 1986 (when endoscopies were first assessed) through 2008 where included in this study. Multivariable logistic regression models for clustered data were used to estimate odds ratios and 95% confidence intervals [OR (95% CIs)].

Results—Among 73,058 participants, 51% (N=37,382) reported ever using OCs. Ever OC use was associated with a slight increase of non-advanced adenomas [OR=1.11 95% CI (1.02, 1.21)] but not with any other endpoints. Duration of OC use was not associated with adenomas, but longer times since last OC use were associated with increased odds of adenomas [e.g., compared to never use, 15+ years since last use: OR=1.17 (1.07, 1.27)]. Shorter times since last OC use were inversely associated [e.g., ≤4 years since last use: OR=0.74 (0.65, 0.84)].

Conclusions—We observed a modest borderline increase in risk of colorectal adenomas with any prior OC use. Additionally, more recent OC use may decrease risk while exposure in the distant past may modestly increase risk of adenomas.

Background—It remains unclear if oral contraceptive (OC) use is associated with the incidence of colorectal cancer. Few studies have examined this association by duration of OC use, time since last OC use, and different cancer subsites.

Methods—Among 88,691 participants of the Nurses’ Health Study I (NHSI) and 93,080 participants of the Nurses’ Health Study II (NHSII), we assessed OC use every 2 years between 1976-2010 and categorized it as ever use, duration of use, and time since last use. We included incident colorectal cancer cases through 2010 (NHSI: age at diagnosis=36-88, N=1,764, NHSII: age at diagnosis=33-64, N=206). Multivariable hazard ratios and 95% confidence intervals [HR (95% CIs)] were estimated using Cox proportional hazards regression models.

Results—Ever OC use was not associated with colorectal cancer in NHSI [1.01 (0.91, 1.12)] nor NHSII [1.03 (0.69, 1.53)]. In NHSII, when compared to never-users, longer durations (5+ years)of OC use were inversely associated with the risk of colon cancers (test for trend p=0.02) but the number of endpoints was limited. No other colorectal cancer subsites were associated with OC durations or times since last OC use in either cohort.

Conclusions—In two large prospective cohorts, we found little evidence that OC use may be protective for colorectal cancer, except potentially with longer durations of use among younger women. Impact—Our results do not support the previous initial studies that reported an inverse association of recent OC use with colorectal cancer but instead support newer, larger studies demonstrating no such association.

Objective: To determine whether use of oral contraceptives is associated with all cause and cause specific mortality.

Design: Prospective cohort study.

Setting: Nurses’ Health Study, data collected between 1976 and 2012.

Population: 121 701 participants were prospectively followed for 36 years; lifetime oral contraceptive use was recorded biennially from 1976 to 1982.

Main outcome measures: Overall and cause specific mortality, assessed throughout follow-up until 2012. Cox proportional hazards models were used to calculate the relative risks of all cause and cause specific mortality associated with use of oral contraceptives.

Results: In our population of 121 577 women with information on oral contraceptive use, 63 626 were never users (52%) and 57 951 were ever users (48%). After 3.6 million person years, we recorded 31 286 deaths. No association was observed between ever use of oral contraceptives and all cause mortality. However, violent or accidental deaths were more common among ever users (hazard ratio 1.20, 95% confidence interval 1.04 to 1.37). Longer duration of use was more strongly associated with certain causes of death, including premature mortality due to breast cancer (test for trend P<0.0001) and decreased mortality rates of ovarian cancer (P=0.002). Longer time since last use was also associated with certain outcomes, including a positive association with violent or accidental deaths (P=0.005).

Conclusions: All cause mortality did not differ significantly between women who had ever used oral contraceptives and never users. Oral contraceptive use was associated with certain causes of death, including increased rates of violent or accidental death and deaths due to breast cancer, whereas deaths due to ovarian cancer were less common among women who used oral contraceptives. These results pertain to earlier oral contraceptive formulations with higher hormone doses rather than the now more commonly used third and fourth generation formulations with lower estrogen doses.