title: What does the mean menarcheal age mean?-An analysis of temporal pattern in variability in a historical swiss population from the 19th and 20th centuries.
abstract: Age at menarche is one of the most important factors when observing growth and development. The aim of this study was to assess the temporal pattern in variability of menarcheal age for a historic Swiss population from the 19th and 20th centuries.
  
  
  
  Medical health records from the Bernese women's hospital (Switzerland) were analyzed. From 10,081 women of a historical Swiss population (born from 1815 to 1954), menarcheal age was calculated. A possible decline in average menarcheal age and variance and skewness were analyzed with the use of descriptive statistics, generalized additive models, and correlation.
  
  
  
  Mean menarcheal age declined from 17.34 years (n = 358) around 1830 to 13.80 years (n = 141) around 1950. Within-cohort variance decreased from 7.5 to 2.1 year(2) . Skewness was negatively correlated with birth year (r = -0.58).
  
  
  
  This study provided evidence for a secular trend in various statistical parameters for age at menarche since the 19th century. Furthermore, the results of the analysis of temporal pattern in variability revealed that the secular trend in menarcheal age happened in two phases. Am. J. Hum. Biol. 28:705-713, 2016. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Biochemistry and Biology; Human Biology, University of Potsdam, Maulbeerallee 2a 14469, Potsdam, Germany. andreleh@uni-potsdam.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Lehmann
authors.affiliation: Biochemistry and Biology; Human Biology, University of Potsdam, Maulbeerallee 2a 14469, Potsdam, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Scheffler
mesh_terms: D000293:Adolescent; D000367:Age Factors; D005260:Female; D006801:Humans; D008572:Menarche; D012189:Retrospective Studies; D013557:Switzerland