title: The length of perimenopausal menstrual cycles increases later and to a greater degree than previously reported.
abstract: OBJECTIVE
  To demonstrate that the perimenopausal increase in menstrual cycle length presented by Treloar et al. was biased by misidentified menopause dates, mean values classified by calendar year, and exclusion of menstrual cycles straddling two calendar years; and to use the revised data to investigate women's experiences of longer perimenopausal cycles.
  
  
  METHODS
  Secondary analysis of prospectively collected menstrual cycle data.
  
  
  METHODS
  Center for Population and Health, Georgetown University.
  
  
  METHODS
  One hundred twenty white, college-educated, US women in the Tremin Research Program on Women's Health.
  
  
  METHODS
  None.
  
  
  METHODS
  Mean cycle length and time spent in >40-day cycles, by year before menopause.
  
  
  RESULTS
  Mean estimates for each of the 4 years before menopause were 30.48, 35.02, 45.15, and 80.22 days, respectively, compared with the original analysis: 33.60, 43.91, 55.87, and 54.58 days. In the year before menopause, the majority of women spent >or=75% of their time in cycles >40 days long.
  
  
  CONCLUSIONS
  Treloar's estimates of mean cycle length were biased. Long cycles occurred throughout perimenopause, but the largest increase in mean cycle length did not occur until the final year before menopause. New estimates of the time spent in cycles >40 days may be useful clinically as well as epidemiologically for assessing menopausal onset and symptomatology.
authors.affiliation: Center for Population and Health, Georgetown University, Washington, DC 20057-1197, USA. rebeccajferrell@gmail.com
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Ferrell
authors.forename: James A
authors.initials: JA
authors.lastname: Simon
authors.forename: Steven M
authors.initials: SM
authors.lastname: Pincus
authors.forename: Germán
authors.initials: G
authors.lastname: Rodríguez
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: O'Connor
authors.forename: Darryl J
authors.initials: DJ
authors.lastname: Holman
authors.forename: Maxine
authors.initials: M
authors.lastname: Weinstein
mesh_terms: D000328:Adult; D017677:Age Distribution; D002986:Clinical Trials as Topic; D015331:Cohort Studies; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D008597:Menstrual Cycle; D008875:Middle Aged; D047648:Perimenopause; D010507:Periodicity; D012189:Retrospective Studies; D013997:Time Factors; D014481:United States / Q000453:epidemiology; D016387:Women's Health