Secular trend in age at menarche in women in Portugal born between 1920 and 1992: Results from three population-based studies

A Century of Change: Unraveling the Impact of Socioeconomic/Historical Milestones on Age at Menarche and Other Female Reproductive Factors in Japan

BACKGROUND

Reproductive factors, such as age at menarche, are known to be associated with disease risk, but data on trends in these factors in Japan are limited. In this study, we investigated secular trends in reproductive factors and explored their potential association with socioeconomic and historical events.

METHODS

We conducted a retrospective analysis of 62,005 Japanese women born between 1890 and 1991 using a survey conducted over 25 years. Trends in reproductive factors were analyzed using linear and joinpoint regression models, and their associations with major historical events involving Japan were evaluated.

RESULTS

We found that the age at menarche showed a significant downward trend (P < 0.001) over the century. Three joinpoints were identified, in 1932 (15.23 years old), 1946 (13.48 years old), and 1959 (12.71 years old), which indicated that average age at menarche decreased by approximately 0.8% per year between 1932 and 1946, and then by 0.4% per year between 1946 and 1959, both of which were statistically significant. However, after 1959, age of menarche remained stable. Analyses of other reproductive factors found significant changes, including a decrease in parity and the number of babies breastfed, and an increase in age at first birth.

CONCLUSION

Age at menarche showed a long-term downward trend in Japan, with significant change points in annual percent change. Other factors showed secular changes in trends as well. These change points were observed at the same time as historical events, namely wars and economic development, suggesting that socioeconomic and environmental changes at the population level affect reproductive factors in females.

Trends in age at menarche from 1943 through 1989 in Taiwan: A retrospective population-based analysis

BACKGROUND

Recent studies have demonstrated a global decline in the age at menarche. Our study aimed to determine the age at menarche of Taiwanese women born between 1943 and 1989.

METHODS

Data were obtained from the Taiwan Biobank. To view the trends in age at menarche, we analyzed data from 74,799 women. The mean, standard deviation, and annual percentage change in age at menarche were calculated for birth-year cohorts.

RESULTS

The mean age at menarche of Taiwanese women born in 1943 was 14.85 years. The age at menarche decreased to 12.20 years for those born in 1989. The mean age at menarche declined by 2.65 years across the 47-year study period; hence, the reduction rate was 0.56 years per decade. This study demonstrated a downward secular trend in the age at menarche of Taiwanese women born between 1943 and 1989. This trend occurred in three stages of decline: fast (1943-1953), slow (1953-1965), and moderate (1965-1989).

CONCLUSION

The age at menarche decreased by 2.65 years among Taiwanese women born in 1943 compared with those born in 1989. This decline occurred in three stages: fast (1943-1953), slow (1953-1965), and moderate (1965-1989). This significant downward secular trend in age at menarche reflects Taiwan's socioeconomic development.

The influence of migration factor on the establishment of menstrual function in girls

The problems of migration are becoming increasingly important and have primary impact on women’s and children’s health. The aim of the study was to evaluate the influence of migration factor on the establishment of menstrual function in girls. The study enrolled 1,222 female undergraduate students of Moscow universities, born in 1995–2000, of diverse ethnicity. The data were collected in 2015–2020 by questionnaire method. The main group included 322 students classified as migrants and the comparison group included 900 students of local origin (Muscovites). Statistical processing of the data was carried out using Statistica 10.0 package (StatSoft; USA). Mean age at menarche constituted 151.35 ± 1.20 months in migrants and 150.88 ± 1.06 months in Muscovites (p > 0.05). For all participants, menarcheal age fell within the range of 11–15 years (normal). Other parameters of menstrual function were also similar between the groups and comparable to corresponding data collected in other countries.