Correlates of age at menarche among sixth grade students in Wisconsin.

We conducted a cross-sectional, school-based survey of sixth-grade girls living in the Reedsburg, Wis area school district to explore factors associated with age at menarche. Data collection included parent and student questionnaires for demographic, menstrual, physical activity, and nutritional information. School nurses conducted physical examinations to provide anthropometric measurements. Salivary samples were obtained for laboratory analysis of estradiol, estrone, estriol, and progesterone levels. Students (n=59) were an average of 11.9 years of age (range: 10-13). Nineteen students (32%) reported menarche, with an average of 11.4 years of age (range: 8-12). Cycle length of the menstruating students averaged 32.0 days (range: 25-46 days). Students' age at menarche was positively correlated with their mothers' age at menarche (r=0.53, P=0.02). Total caloric intake, macronutrients, hormone levels, birthweight, and family size were not associated with menstrual status. We observed an inverse association between increasing weight and earlier age at menarche (P=0.03). Students past menarche watched more television (P=0.03) and participated in fewer hours of sporting activity (P=0.08) than students who had not yet reached menarche. These preliminary data suggest that further investigation of the determinants of menarche is both feasible and warranted.