Variations in the age of onset of menarche among inhabitants of rural and urban areas in Delta State, South-South Nigeria Original paper

What was studied?

This original research study investigated the variations in the age of onset of menarche among female adolescents living in rural and urban areas of Delta State, South-South Nigeria. The primary objective was to determine the average age of menarche in the population and to ascertain whether place of residence (urban vs. rural) and socioeconomic status significantly influence the timing of menarche. The study also sought to establish baseline data for age at menarche in this specific region and compare these findings with previously reported data from other regions, thereby contributing to the understanding of environmental and demographic influences on female pubertal development. Although the research did not directly assess the microbiome, the focus keyphrase “age of menarche and microbiome associations” is relevant, as emerging literature increasingly links pubertal timing with the composition and function of the gut and reproductive tract microbiomes.

Who was studied?

The study population comprised 510 female students from six junior secondary schools (JSS 1–3), aged 8 to 16 years, in Ughelli Local Government Area, Delta State, Nigeria. Participants were selected through random sampling, with 85 students from each school. All participants were age-matched and met inclusion criteria that required consent and the ability to recall their age at menarche. Of the total, 243 students had already attained menarche, 130 from urban and 113 from rural settings. The socioeconomic status of each participant was classified into five classes based on a modified Oyedeji scale, accounting for parental occupation and education, among other factors.

Most important findings

The key finding was a statistically significant difference in the mean age of menarche between urban and rural dwellers. The mean age of menarche for the overall cohort was 12.68 ± 1.37 years. Urban girls experienced menarche earlier compared to their rural counterparts, with a p-value <0.05 indicating significance. In both settings, the most frequent age of menarche differed: 12 years in urban areas and 13 years in rural areas. Socioeconomic status also had a notable impact. Girls from higher socioeconomic classes (Upper Class I and II) reached menarche earlier than those from lower classes, a trend more pronounced in urban areas. For instance, in urban Upper Class I, mean age at menarche was 11.45 years, while in urban Middle Class III it was 12.76 years. Analysis of variance confirmed significant differences in menarcheal age across socioeconomic strata in both urban and rural cohorts.

Key implications

The study’s findings have important clinical and public health implications. Earlier menarche in urban and higher socioeconomic groups may signal underlying shifts in nutritional status, environmental exposures, and possibly microbiome composition, all of which are risk factors for various chronic diseases later in life, including breast cancer, cardiovascular disease, and metabolic syndromes. For clinicians, recognizing these demographic trends is crucial for anticipatory guidance, risk assessment, and targeted education regarding reproductive health and disease prevention. This data also underscores the importance of further research into the role of the microbiome in pubertal timing, as changes in diet, environment, and socioeconomic status may influence both the microbiome and the endocrine system, contributing to observed variations in menarcheal age.