Early- Life Determinants of the Age at Menarche.

Abstract

Menarche, the first menstrual period, is a recognizable marker of puberty. The timing of menarche has important public health ramifications because an early age at menarche is associated with breast and endometrial cancers, obesity, type II diabetes, cardiovascular disease, and all-cause mortality. Secular trends and between-country variability in age at menarche suggest that the onset of puberty is responsive to changing environmental conditions. Nevertheless, the specific environmental factors that influence age at menarche remain largely unidentified. In this dissertation we first examined sociodemographic influences on recent trends in age at menarche using nationally-representative data from Colombia, finding that there was a recent ongoing negative trend in the age at menarche, most pronounced in higher socioeconomic status girls and among those living in urban areas. In the second aim we utilized the nationally representative dataset to examine the role of prenatal factors including season and altitude on menarche. We found that a higher number of gestation days exposed to the rainy season was related to an earlier age at menarche whereas a higher altitude of residence was related to a later age at menarche. We also noted that the association between gestation days exposed to the rainy season and altitude was only apparent among girls living in altitudes ≥2000 m. Finally, in the third aim we examined the relation between childhood red meat intake frequency and age at menarche in a longitudinal study among 456 school-aged girls from Bogotá, Colombia. We found that higher red meat intake frequency at 5-12 y was associated with an earlier age at menarche. We also incidentally discovered that higher frequency of tuna/sardine intake during childhood was related to later ages at menarche. In summation, this dissertation research shows that the age at menarche is responsive to early life environmental correlates including changing socioeconomic conditions, perinatal climate and geographic factors, and diet during childhood. This provides impetus to elucidate the specific mechanisms underlying these associations, which could ultimately lead to interventions aimed at promoting optimal pubertal development.