Early age at menarche is associated with insulin resistance: a systemic review and meta-analysis

Objectives: We aimed to conduct a systemic review and meta-analysis of the relevant studies to further investigate the association between age at menarche and insulin resistance. Methods: PubMed, EMBASE, and Web of Science (SCI) databases were systemically searched until December 2017. Observational studies comparing the incidences of insulin resistance in patients with early, average, and late menarchal ages were identified. Weighted mean difference (WMD) for HOMA-IR scores and fasting serum insulin levels in early vs late, early vs average. and average vs late comparisons were calculated with a random- or fixed-effects model. Results: A total of eight articles involving 5504 subjects were finally included. In the analysis of HOMA-IR, the pooled WMDs in five studies were 0.45 (95% confidence interval [CI] 0.31-0.60, p < 0.001), 0.40 (95% CI 0.28-0.52, p < 0.001), and -0.01 (95% CI -0.09 to 0.07, p = 0.854) for early vs late, early vs average, and average vs late comparisons, respectively. The fasting serum insulin levels in eight studies were analyzed, and it was significantly higher in subjects with earlier age at menarche (WMD 1.28, 95% CI 0.92-1.63, p < 0.001 for early vs late comparison, WMD 1.28, 95% CI 1.13-1.43, p < 0.001 for early vs average comparison) with mild and acceptable heterogeneity (I-2 = 42.5% and 7.4%, respectively). Publication bias was not detected via funnel plots and Egger's tests. Conclusions: Our study revealed that earlier age at menarche was significantly associated with insulin resistance.