title: Nongenetic determinants of age at menarche: a systematic review.
abstract: BACKGROUND
  The acceleration of pubertal development is an important medical and social problem, as it may result in increased morbidity and mortality in later life. This systematic review summarizes relevant data about nongenetic factors, which contribute to age at menarche (AAM), and suggests those which may be the most important.
  
  
  METHODS
  The available literature from 1980 till July 2013 was searched using PubMed and Google Scholar databases. Finally, 154 papers were selected for the analysis.
  
  
  RESULTS
  Environmental factors, which may affect AAM, vary in populations of different ethnicity. The prenatal, infancy, and early childhood periods are the most susceptible to these factors. Body weight, high animal protein intake, family stressors (e.g., single parenting), and physical activity seem to influence AAM in most populations.
  
  
  CONCLUSIONS
  The data about influence of nongenetic factors on AAM are still inconsistent. The factors affecting prenatal and early childhood growth seem to have a larger effect on further sexual maturation. Further studies are needed in order to validate the association between other environmental determinants and AAM in different ethnical groups.
authors: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Pokfulam, Hong Kong.
authors: Anna
authors: 0000-0003-4977-4894
authors: A
authors: Yermachenko
authors: School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Pokfulam, Hong Kong.
authors: Volodymyr
authors: 0000-0002-2535-103X
authors: V
authors: Dvornyk
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001724:Birth Weight; D001942:Breast Feeding; D002648:Child; D005006:Ethnicity; D005260:Female; D006801:Humans; D008572:Menarche / Q000235:genetics* / Q000523:psychology; D009043:Motor Activity; D011247:Pregnancy; D015430:Weight Gain