ABSTRACT
Age at menarche and its associated factors are reported for 1862 Shiraz [Southern Iran] secondary school girls taking part in a cross-sectional survey selected from four educational districts of the city. Probit analysis was used to estimate age at menarche, principal component analysis [PCA] was applied to analyze socio-economic status [SES]. Body mass index [BMI] was used as an indicator of nutrition. Mean +/- SD age at menarche 12.91 +/- 1.23 years [95% CI: 12.84-12.97]. Of all subjects, 33.7% first menstruated in summer. 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. It is concluded that BMI and SES had the most significant effects on variation of the menarcheal age in a unified statistical model. However, their interaction was found to be not statistically significant