Department of Epidemiology & Biostatistics, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran.
PLoS One. 2012;7(12):e51446. doi: 10.1371/journal.pone.0051446. Epub 2012 Dec 7.
There is no universal consensus on the relationship between body mass index (BMI) and breast cancer. This meta-analysis was conducted to estimate the overall effect of overweight and obesity on breast cancer risk during pre- and post-menopausal period.
All major electronic databases were searched until April 2012 including Web of Knowledge, Medline, Scopus, and ScienceDirect. Furthermore, the reference lists and related scientific conference databases were searched.
All prospective cohort and case-control studies investigating the association between BMI and breast cancer were retrieved irrespective of publication date and language. Women were assessed irrespective of age, race and marital status. The exposure of interest was BMI. The primary outcome of interest was all kinds of breast cancers confirmed pathologically. Study quality was assessed using the checklist of STROBE. Study selection and data extraction were performed by two authors separately. The effect measure of choice was risk ratio (RR(i)) and rate ratio (RR(a)) for cohort studies and odds ratio (OR) in case-control studies.
Of 9163 retrieved studies, 50 studies were included in meta-analysis including 15 cohort studies involving 2,104,203 subjects and 3,414,806 person-years and 35 case-control studies involving 71,216 subjects. There was an inverse but non-significant correlation between BMI and breast cancer risk during premenopausal period: OR = 0.93 (95% CI 0.86, 1.02); RR(i) = 0.97 (95% CI 0.82, 1.16); and RR(a) = 0.99 (95% CI 0.94, 1.05), but a direct and significant correlation during postmenopausal period: OR = 1.15 (95% CI 1.07, 1.24); RR(i) = 1.16 (95% CI 1.08, 1.25); and RR(a) = 0.98 (95% CI 0.88, 1.09).
The results of this meta-analysis showed that body mass index has no significant effect on the incidence of breast cancer during premenopausal period. On the other hand, overweight and obesity may have a minimal effect on breast cancer, although significant, but really small and not clinically so important.
体重指数（BMI）与乳腺癌之间的关系尚无定论。本荟萃分析旨在评估超重和肥胖与绝经前和绝经后乳腺癌风险之间的总体关系。
检索了所有主要电子数据库，包括 Web of Knowledge、Medline、Scopus 和 ScienceDirect，截至 2012 年 4 月。此外，还检索了参考文献列表和相关科学会议数据库。
检索了所有前瞻性队列研究和病例对照研究，无论研究日期和语言如何，均观察 BMI 与乳腺癌之间的关系。研究对象为女性，无论年龄、种族和婚姻状况如何。感兴趣的暴露因素为 BMI。主要观察指标为经病理证实的各种乳腺癌。使用 STROBE 清单评估研究质量。由两名作者分别进行研究选择和数据提取。选择的效应量为队列研究的风险比（RR(i)）和率比（RR(a)）以及病例对照研究的比值比（OR）。
在 9163 篇检索文献中，有 50 篇文献纳入荟萃分析，其中包括 15 项队列研究，共涉及 2104203 名受试者和 3414806 人年，以及 35 项病例对照研究，共涉及 71216 名受试者。在绝经前，BMI 与乳腺癌风险呈负相关，但无统计学意义：OR=0.93（95%CI，0.86-1.02）；RR(i)=0.97（95%CI，0.82-1.16）；RR(a)=0.99（95%CI，0.94-1.05）；而在绝经后，BMI 与乳腺癌风险呈正相关且有统计学意义：OR=1.15（95%CI，1.07-1.24）；RR(i)=1.16（95%CI，1.08-1.25）；RR(a)=0.98（95%CI，0.88-1.09）。
本荟萃分析结果表明，BMI 对绝经前乳腺癌的发生率无显著影响。另一方面，超重和肥胖可能对乳腺癌有轻微影响，尽管有统计学意义，但实际上很小，且在临床上并不重要。
