title: Long-term secular trends in the age at menarche in Israel: a systematic literature review and pooled analysis.
abstract: OBJECTIVE
  A worldwide decline in the age at menarche (AAM) has been reported in recent decades. This trend has been also clinically observed among Israeli women and was reported in our previous study.
  
  
  METHODS
  We reviewed the literature reporting the mean AAM in Israel during the past century. Studies were excluded if participants had been investigated due to illness or any condition which could affect sexual maturation. Mean AAM was analyzed using a simple linear regression weighted for number of participants in each birth cohort and stratified to birth cohorts before and after 1970, based on the outcome of our previous study.
  
  
  RESULTS
  AAM varied little among women born between 1875 and 1970, but there was a clear downwards trend from 13.4 in 1970 to 12.8 two decades later. In a stratified analysis we found a significant negative association between birth year and AAM in the birth cohort after 1970 (standardized β coefficient = -0.94 per year, R(2) = 0.87; p < 0.001).
  
  
  CONCLUSIONS
  These results suggest a significant decline in mean AAM in Israeli women born in 1970 or later.
authors: Medical Division, Maccabi Healthcare Services, Tel Aviv University, Tel Aviv, Israel.
authors: Shira
authors: S
authors: Flash-Luzzatti
authors: Clara
authors: C
authors: Weil
authors: Varda
authors: V
authors: Shalev
authors: Tal
authors: T
authors: Oron
authors: Gabriel
authors: G
authors: Chodick
mesh_terms: D000293:Adolescent; D041923:Adolescent Development / Q000502:physiology*; D000367:Age Factors; D017668:Age of Onset; D002648:Child; D005260:Female; D006801:Humans; D007557:Israel; D008572:Menarche / Q000502:physiology*; D011627:Puberty / Q000502:physiology*