Diet, body size and menarche in a multiethnic cohort

A multiethnic cohort of 1378 Southern California school girls aged 8-13 yea rs was followed for 4 years to evaluate factors predicting age at menarche, a risk factor for breast cancer. Height and weight were measured and dieta ry intake was assessed using a semi-quantitative food frequency questionnai re. Of 939 girls providing data on menarcheal status, 767 were premenarchea l at the start of the study; 679 girls provided acceptable dietary data and were included in the analyses. Cox proportional hazards models were used t o assess the relationship between diet, body size, ethnicity and age at men arche. Hispanic, Asian/Pacific Island and African-American girls were more likely to experience early menarche than non-Hispanic white girls. Tall (> 148.6 cm) Versus short (< 135.9 cm) girls experienced earlier menarche (rel ative hazard (RH) = 2.9, 95% confidence interval (CI) 2.1-4.1) as did those with high Quetelet's index (QI, kg m(-2)) (> 20.7) Versus low QI (< 16.1) (RH = 2.2, 95% CI 1.7-2.9). Of all the dietary variables analysed, only ene rgy intake was related to age at menarche. High Versus low energy intake (> 12 013 kJ vs < 7004 kJ) was associated with a delay in menarche (RH = 0.7, 95% CI 0.5-0.9); this finding was limited to a subset of heavy Hispanic gi rls who appeared to underreport their dietary intake.