Menarche at an Earlier Age: Results from Two National Surveys of Israeli Youth, 2003 and 2016

Abstract

To assess emergent changes in the age at menarche and investigate associated factors in Israeli adolescents in 2003 and2016. Cross-sectional study. Two national representative school-based surveys (first and second "Mabat Youth"). Both surveys included female students in 7th-12th grades (ages 11-19years). The first (N=3328) was conducted between the years 2003 and 2004, and the second (N=2535) from 2015 to2016. The survey questionnaire was self-administered and anthropometric measurements were performed by trained personnel. The current age at menarche in Israeli girls was determined and independent factors (demographic, clinical, and lifestyle) examined. Changes that occurred since the past national survey more than a decade ago were documented. The estimated median age at menarche declined from 13.0 (interquartile range, 12.0-14.0) years in 2003-2004 to 12.5 (interquartile range, 12.0-13.0) years in 2015-2016 (P<.0001). Jewish girls reached menarche earlier than Arab girls, but both populations experienced a similar downward trend in the past approximately 14years. Greater body mass index, higher socioeconomic status, and immigrant status were associated with younger menarche onset (P<.001). Age at menarche remained lower in 2015-2016 vs 2003-2004, even after adjustment for these potential confounders, with a high hazard ratio (HR), which decreased as a function of survival time (t): HRt=15.417×0.813t. This study confirms the decline in age at menarche in Israel. Findings were associated with body mass index and population group but also indicated that other factors are likely involved.