AGE AT MENARCHE IN PERUVIAN GIRLS AT SEA-LEVEL AND AT HIGH-ALTITUDE -EFFECT OF ETHNIC-BACKGROUND AND SOCIOECONOMIC-STATUS

The objective of the present study was to determine median age at mena rche using the status quo method and the independent effects of ethnic background and socioeconomic status on the age at menarche in Peruvia n girls from two distinct levels of altitude: Lima (150 m) and Cerro d e Pasco (4,340 m). The sample included 503 girls from Lima and 625 gir ls from Cerro de Pasco, ages 10-18 years. Ethnic background was determ ined by four parental surnames. Subjects were classified as Quechua wh en one or more surnames were from Quechua origin and Spanish when four surnames were from Spanish origin. Socioeconomic status was determine d using a socioeconomic index score and subjects were classified as be longing to the middle-low, low, or very low class. Median age at menar che was calculated by survival analysis using the Life Table Method wi th a 95% Confidence Interval (CI). Among Quechua and Spanish girls, ag e at menarche occurred later at high altitude than at sea level. Media n ages at menarche for the over all groups were 13.08 (12.91-13.25, 95 % CI) years in Lima and 14.33 (14.17-14.48, 95% CI) years in Cerro de Pasco (P < 0.0001). Socioeconomic status had no significant effect on menarcheal age (P > 0.05). Controlling socioeconomic status in the des ign, median age at menarche was still higher at high altitude than at sea level (P < 0.05). After logistic regression analysis, an effect on age at menarche of chronological age and place of residence was obser ved, but not by ethnic background, socioeconomic status and not by int eractions of age and place of residence, age and socioeconomic status, place of residence and socioeconomic status, place of residence and e thnic background, or socioeconomic status and ethnic background. Thus later age at menarche observed in girls at high altitude is not due to differences in ethnicity or socioeconomic status. (C) 1996 Wiley-Liss , Inc.