Associations of parity and age at first pregnancy with overall and cause-specific mortality in the Cancer Prevention Study II

Objective To evaluate the association of parity, number of live births, and age at first birth with mortality using multivariable-adjusted Cox proportional hazards regression models. Design Observational cohort. Setting Not applicable. Patient(s) A total of 424,797 women. Intervention(s) None. Main Outcome Measure(s) All-cause and cause-specific mortality. Result(s) During median follow-up of 24.93 years, 238,324 deaths occurred. Parous, compared with nulliparous, women had lower rates of all-cause (hazards ratio [HR] = 0.94, 95% confidence interval [CI] 0.93–0.96) mortality, driven by heart disease and overall cancer mortality. A linear trend was found for more births and diabetes mortality (P<.001) with having ≥6 births, compared with 2, associated with an HR of 1.28 (95% CI 1.15–1.43). Compared with age at first birth from 20–22 years, age at first birth <20 years was associated with higher mortality rates overall (HR = 1.04, 95% CI 1.02–1.06), driven by heart disease and chronic obstructive pulmonary disease mortality; whereas, ≥35 years was associated with higher overall cancer mortality (HR = 1.13, 95% CI 1.06–1.20). Conclusion(s) Although parity was associated with a slight reduction in rates of all-cause mortality resulting in a minimal impact on average lifespan, the higher diabetes mortality in grand multiparous women might warrant continuous monitoring, particularly for abnormal glucose metabolism, among these women.