title: Effects of a school-based obesity-prevention intervention on menarche (United States).
abstract: OBJECTIVE
  Early menarche is a risk factor for breast cancer. Since body composition influences age at menarche we decided to estimate the effects of a school-based intervention for the prevention of obesity on the initiation of menses in young girls.
  
  
  METHODS
  Ten schools were randomized to a modified curriculum or no curricular changes for 2 school-years. Data of 508 pre-menarcheal girls at baseline (age range: 10-13 years) were analyzed.
  
  
  RESULTS
  Girls attending an intervention school experienced menarche less frequently than girls attending control schools during the intervention period (intervention schools = 54%, control schools = 59%; RR = 0.76; 95% CI [0.66, 0.87]). Attending an intervention school was also associated with lower increase in BMI (-0.3 kg/m2; p = 0.003), lower gains in triceps skinfold thickness (-1.5 mm; p = 0.007), decreased television viewing (-0.6 h/day; p<0.0001) and increased physical activity (3.1 MET-h/week; p = 0.032). Including these changes as predictors of menarche incidence attenuated the intervention effect (RR = 0.94; 95% CI [0.80, 1.10]).
  
  
  CONCLUSIONS
  The intervention delayed menarche in this group of girls. The delay was produced by increased physical activity, reduced television viewing and changes in BMI and fat distribution. These findings may have implications for the primary prevention of breast cancer.
authors.affiliation: Department of Nutrition, Harvard School of Public Health, 665 Huntington Ave., Boston, MA 02115, USA.
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Chavarro
authors.forename: Karen E
authors.initials: KE
authors.lastname: Peterson
authors.forename: Arthur M
authors.initials: AM
authors.lastname: Sobol
authors.forename: Jean L
authors.initials: JL
authors.lastname: Wiecha
authors.forename: Steven L
authors.initials: SL
authors.lastname: Gortmaker
mesh_terms: D000293:Adolescent; D001827:Body Height; D015992:Body Mass Index; D001900:Boston / Q000453:epidemiology; D002648:Child; D003479:Curriculum; D005260:Female; D005500:Follow-Up Studies; D015438:Health Behavior; D006801:Humans; D016014:Linear Models; D008572:Menarche; D009043:Motor Activity; D009765:Obesity / Q000517:prevention & control*; D012572:School Health Services; D012885:Skinfold Thickness; D013690:Television; D013997:Time Factors