Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
Eur Urol. 2013 Apr;63(4):733-8. doi: 10.1016/j.eururo.2013.01.005. Epub 2013 Jan 11.
The incidence of bladder cancer (BCa) is substantially lower in women than in men, a difference that cannot be fully explained by established risk factors. Several studies suggest that hormonal and reproductive factors play a role in the development of BCa.
To examine possible associations between patterns of childbearing and the risk of BCa.
DESIGN, SETTING, AND PARTICIPANTS: This cohort study encompassed >2 million women for whom information on reproductive history and BCa incidence was retrieved from Swedish population-based registers.
Incidence rate ratios (IRRs) of BCa were estimated using Cox proportional hazards modelling. The exposures under investigation were parity and age at first birth, adjusted for education and history of chronic obstructive lung disease (COLD).
Among 2 009 811 women in the cohort, 2860 incident cases of BCa were identified. Parous women had lower incidence of BCa compared with nulliparous women (adjusted IRR: 0.80; 95% confidence interval [CI], 0.72-0.89). Moreover, the incidence was 15% lower in women with two children and 24% lower in women with three or more children compared with uniparous women. Compared with women aged 20-24 at first childbirth, the incidence was elevated in women with a first birth before age 20 (adjusted IRR: 1.16; 95% CI, 1.05-1.29). The risk of BCa was elevated in women with low education and among women with a history of COLD. Absence of data on menstrual history, use of exogenous hormones, and smoking was a limitation of the study.
The incidence of BCa decreased with increasing parity and older age at first birth. Although smoking habits may partly explain some of the associations, our findings provide support for yet-to-be-identified protective mechanisms associated with childbearing, possibly mediated by hormonal or structural changes following pregnancy.
膀胱癌（BCa）的发病率在女性中明显低于男性，这一差异不能完全用已确定的风险因素来解释。几项研究表明，激素和生殖因素在 BCa 的发展中起作用。
研究生育模式与 BCa 风险之间的可能关联。
设计、环境和参与者：这项队列研究涵盖了超过 200 万女性，从瑞典基于人群的登记处检索到了她们的生育史和 BCa 发病信息。
使用 Cox 比例风险模型估计 BCa 的发病率比值（IRR）。研究中的暴露因素是生育次数和首次分娩年龄，调整了教育程度和慢性阻塞性肺疾病（COLD）病史。
在队列中的 2009811 名女性中，确定了 2860 例 BCa 发病病例。与未生育的女性相比，生育过的女性 BCa 的发病率较低（调整后的 IRR：0.80；95%置信区间[CI]，0.72-0.89）。此外，与生育一次的女性相比，生育两次的女性发病率降低 15%，生育三次或更多次的女性发病率降低 24%。与首次生育年龄在 20-24 岁的女性相比，首次生育年龄在 20 岁以下的女性发病率升高（调整后的 IRR：1.16；95%CI，1.05-1.29）。低教育程度和患有 COLD 病史的女性患 BCa 的风险增加。缺乏关于月经史、外源性激素使用和吸烟的数据是该研究的一个局限性。
BCa 的发病率随着生育次数的增加和首次生育年龄的增加而降低。尽管吸烟习惯可能在一定程度上解释了部分关联，但我们的研究结果为与生育有关的尚未确定的保护机制提供了支持，这可能与怀孕后的激素或结构变化有关。
