Abstract
Evidence between age at menarche and endometrial cancer risk have been controversial. Therefore, we conducted a meta-analysis of prospective studies to analyze the aforementioned association. Relevant studies were identified by searching PubMed and EMBASE databases until the end of June 2015. A random-effects model was used to estimate summary relative risks (RRs) and 95% confidence intervals (CIs) for associations between menarcheal age and endometrial cancer risk. Our meta-analysis included eight prospective studies involving 4553 subjects with endometrial cancer. The summarized RRs of endometrial cancer for menarcheal age were 0.68 (95%CI = 0.58–0.81, I2 = 41.9%, P = 0.099, n = 8) when comparing women with oldest category of menarcheal age with women with youngest category of menarcheal age. Notably, there was an 4% reduction in risk for per 2 years delay in menarcheal age (summarized RR = 0.96; 95%CI = 0.94–0.98, I2 = 45.7%, P = 0.101, n = 6). Additionally, significant inverse associations were consistent within all stratified analyses. There was no evidence of publication bias or significant heterogeneity between subgroups detected by meta-regression analyses. Our findings support the hypothesis that late menarcheal age is inversely associated with endometrial cancer risk. Further larger prospective or pooled studies are warranted to fully adjust for potential confounders and distinguish whether the associations differ by histological subtypes of endometrial cancer.
Highlights
Longer lifetime exposure to endogenous estrogen and progesterone deficiency associated with anovulatory cycles[19,20,21], the evidence from observational studies are conflicting, which might be partly attributed to different study designs and limited sample sizes of individual studies
The association between hormonal risk factors and endometrial cancer risk could be partly attributed to the “unopposed estrogen” hypothesis
As the beginning of the menstruation span, later menarcheal age might decrease the risk of endometrial cancer by decreasing a woman’s lifetime number of ovulations which was characterized by exposure to endogenous estrogen and progesterone deficiency
Summary
Longer lifetime exposure to endogenous estrogen and progesterone deficiency associated with anovulatory cycles[19,20,21], the evidence from observational studies are conflicting, which might be partly attributed to different study designs and limited sample sizes of individual studies. Minority of these studies provided the detail information of the risk estimation of per year advance/delay in menarcheal age by dose-response analysis. We carried out this meta-analysis of all prospective studies published up to May 2014 to systematically and quantitatively evaluate this issue
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