title: Has age at menarche changed? Results from the National Health and Nutrition Examination Survey (NHANES) 1999-2004.
abstract: OBJECTIVE
  To examine self-reported age at menarche in U.S. adults and the associations between age at menarche and race/ethnicity.
  
  
  METHODS
  Data from 1999-2004 National Health and Nutrition Examination Survey (NHANES) for 6788 females 20 years and over were analyzed. Self-reported age at first menses (in years) by birth year groups is reported overall and for Mexican Americans, non-Hispanic whites, and non-Hispanic blacks.
  
  
  RESULTS
  Mean age at menarche in the United States declined over time from 13.3 years (95% CI: 13.2-13.5) in the oldest age group, those born prior to 1920, to 12.4 years (95% C.I. 12.2-12.5 years) in the youngest group, born between 1980 and 1984. Declines in age at menarche were observed for all race/ethnicity groups. Non-Hispanic black females had the largest decline in mean age at menarche from 13.6 years (95% CI: 13.1-14.1) in women born prior to 1920, to 12.2 years (95% CI: 11.8-12.6) in the 1980-84 birth cohort. Mean age at menarche among non-Hispanic white females declined from 13.3 years (13.1-13.6) in the pre-1920 birth cohort to 12.5 years (12.3-12.8) in the 1980-84 birth cohort.
  
  
  CONCLUSIONS
  Significant declines in the mean age of menarche for U.S. females occurred overall and for all race/ethnic groups examined. Mean age of menarche declined by .9 year overall in women born before 1920 compared to women born in 1980-84; the declines in the mean age at menarche ranged from .7 to 1.4 years depending on the race/ethnicity group.
authors.affiliation: National Center for Health Statistics, Division of Health and Nutrition Examination Surveys, Centers for Disease Control and Prevention, U.S. Department of Health and Human Services, Hyattsville, Maryland 20782, USA. mxm7@cdc.gov
authors.forename: Margaret A
authors.initials: MA
authors.lastname: McDowell
authors.forename: Debra J
authors.initials: DJ
authors.lastname: Brody
authors.forename: Jeffery P
authors.initials: JP
authors.lastname: Hughes
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008572:Menarche; D009749:Nutrition Surveys; D044469:Racial Groups / Q000706:statistics & numerical data; D014481:United States / Q000453:epidemiology