Association of Early Menarche with Adolescent Health in the Setting of Rapidly Decreasing Age at Menarche.

STUDY OBJECTIVE:This study aimed to investigate the association between age at menarche (AAM) and adverse health indicators in adolescent girls. DESIGN:A retrospective cohort study. SETTING:Population-based survey data. PARTICIPANTS:A total of 319,437 female participants aged 12-18 years from the Korea Youth Risk Behaviour Web-based Survey. INTERVENTIONS AND MAIN OUTCOME MEASURES:We assessed associations between AAM (categorized as ≤10, 11, and ≥12) and health indicators (poor self-rated health, high psychological stress, unhappiness, sexual initiation, and pregnancy). Covariates were individual-level (bodyweight, living with family, parent's education, household wealth, and presence of parents and siblings) and community-level factors (year of birth, single-sex education and level of school, urbanization level of school area, year of survey, and regional deprivation). Odds ratios (ORs) for each adverse health indicator were examined by each AAM group using multivariable regression analyses. For pregnancy, we calculated relative risks (RRs) using a log-binomial regression model. RESULTS:Age at menarche was <12 in 42% of our study population. Nearly one-half of the girls born in the early 2000s went through menarche before the age of 12 years, whereas only one-third of girls born in the early 1990s went through menarche before the age of 12 years. Girls who experienced menarche at age ≤10 or age 11 years were more likely to show self-rated poor health (AAM ≤ 10: OR, 1.28; 95% confidence intervals [CI], 1.22-1.34; AAM = 11: OR, 1.16; 95% CI, 1.12-1.21), high stress (OR, 1.19; 95% CI, 1.14-1.23, and OR, 1.10; 95% CI, 1.06-1.14), and sexual initiation (OR, 2.21; 95% CI, 2.05-2.38, and OR, 1.32; 95% CI, 1.23-1.41) compared to those with AAM ≥12 years when data were adjusted for all covariates. AAM ≤10 years was associated with consistently higher odds for poor health than AAM ≥12 years. The ORs of sexual initiation increased with earlier AAM. Risk of pregnancy was similar across AAM groups when individual- and community-level covariates were controlled for. CONCLUSION:Early menarche, defined as <12 years, can be still a useful indicator in adolescent health interventions to identify high-risk groups in the setting of declining AAM.