title: Age at menarche in Iran.
abstract: BACKGROUND
  Age at menarche and its potential associated factors are reported for 1862 Shiraz (Southern Iran) secondary school girls taking part in a cross-sectional survey selected from the four educational districts of the city.
  
  
  METHODS
  Probit analysis was used to estimate age at menarche, principal component analysis (PCA) was applied to analyse socio-economic status (SES). Body mass index (BMI) was used as an indicator of nutrition.
  
  
  RESULTS
  Mean +/- SD age at menarche was 12.91 +/- 1.23 years (95% CI: 12.84-12.97). Of all subjects, 33.7% first menstruated in summer. The highest mean age at menarche was 13.01 years in winter. Stress, anxiety and discomfort was seen among 70.3% of subjects at menarche indicating total or partial ignorance of the menstruation phenomenon. Age at menarche decreased as SES improved. Menarcheal age was delayed for underweight subjects.
  
  
  CONCLUSIONS
  It is concluded that BMI and SES had the most significant effects on variation of menarcheal age in a unified statistical model. However, their interaction was found to be not statistically significant.
authors.affiliation: School of Public Health, Shiraz University of Medical Sciences, Shiraz, Islamic Republic of Iran.
authors.forename: S M T
authors.initials: SM
authors.lastname: Ayatollahi
authors.forename: E
authors.initials: E
authors.lastname: Dowlatabadi
authors.forename: S A R
authors.initials: SA
authors.lastname: Ayatollahi
mesh_terms: D000293:Adolescent; D000367:Age Factors; D017668:Age of Onset; D002648:Child; D005260:Female; D006801:Humans; D007492:Iran; D008572:Menarche / Q000502:physiology*