Department of Obstetrics and Gynecology, Shengjing Hospital, China Medical University, Shenyang, China.
PLoS One. 2013 Sep 30;8(9):e75279. doi: 10.1371/journal.pone.0075279. eCollection 2013.
Association between parity and colorectal cancer (CRC) risk has been investigated by several epidemiological studies but results are controversial, yet a comprehensive and quantitative assessment of this association has not been reported so far.
Relevant published studies of parity and CRC were identified using MEDLINE, EMBASE and Web of Science databases through end of April 2013. Two authors independently assessed eligibility and extracted data. Eleven prospective studies reported relative risk (RR) estimates and 95% confidence intervals (CIs) of CRC risk associated with parity. We pooled the RR from individual studies using fixed- or random-effects models and carried out heterogeneity and publication bias analyses.
The summary RR for the ever parity vs. nulliparous was 0.95 (95% CI: 0.88-1.02), with no heterogeneity (Q = 9.04, P = 0.443, I (2) = 0.5%). Likewise, no significant association was yielded for the highest vs. lowest parity number (RR = 1.02, 95% CI: 0.89-1.17), with moderate heterogeneity (Q = 17.48, P = 0.094, I (2) = 37.1%). Dose-response analysis still indicated no effect of parity on CRC risk and the summary RR of per one livebirth was 0.99 (95% CI: 0.96-1.02), with moderate of heterogeneity (Q = 16.50, P<0.021, I (2) = 57.6%). Similar results were observed among all the subgroup analyses. No evidence of publication bias and significant heterogeneity between subgroups were detected by meta-regression analyses.
Results of this dose-response meta-analysis of prospective studies found that there was little evidence of an association between parity and CRC risk.
几项流行病学研究调查了生育次数与结直肠癌（CRC）风险之间的关系，但结果存在争议，迄今为止，尚未对此相关性进行全面和定量评估。
通过 MEDLINE、EMBASE 和 Web of Science 数据库，截至 2013 年 4 月底，检索了有关生育次数和 CRC 的相关已发表研究。两名作者独立评估了纳入标准并提取了数据。有 11 项前瞻性研究报告了生育次数与 CRC 风险相关的相对风险（RR）估计值和 95%置信区间（CI）。我们使用固定效应或随机效应模型汇总了个体研究的 RR，并进行了异质性和发表偏倚分析。
总生育次数与 nulliparous 相比的汇总 RR 为 0.95（95%CI：0.88-1.02），无显著异质性（Q=9.04，P=0.443，I ²=0.5%）。同样，最高生育次数与最低生育次数之间也没有显著相关性（RR=1.02，95%CI：0.89-1.17），存在中度异质性（Q=17.48，P=0.094，I ²=37.1%）。剂量-反应分析仍表明生育次数与 CRC 风险无关，每生育一次的汇总 RR 为 0.99（95%CI：0.96-1.02），存在中度异质性（Q=16.50，P<0.021，I ²=57.6%）。所有亚组分析均得到类似结果。通过 meta-regression 分析未发现发表偏倚和亚组间显著异质性的证据。
本前瞻性研究的剂量-反应荟萃分析结果表明，生育次数与 CRC 风险之间几乎没有关联。
