Original Study
The Decreasing Age at Menarche in Mexico

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Abstract

Study Objective

To estimate the current age at menarche in 2 urban areas from Mexico and to analyze secular trends in the age at menarche in Mexico City.

Design

Cross-sectional survey and secondary data analyses.

Setting

(1) Samples of female students from Mexico City and from the city of Xalapa; and (2) national health surveys.

Participants

(1) Pre- and postmenarcheal students, aged 8-17 years; and (2) data for women born between 1904 and 1999 who grew up in Mexico City were obtained from 3 relevant national health surveys.

Interventions and Main Outcome Measures

(1) Students were asked if they had had their first period and when it occurred; (2) information on year of birth and age at menarche for the remaining women was obtained from the national surveys; data were divided in groups according to the decade in which the women were born.

Results

(1) The estimated mean age at menarche was 11.40 and 11.34 years in Mexico City and Xalapa respectively. (2) There were significant differences in age at menarche among women who were born in the different decades analyzed. Women who were born in the 1990s or later reported an earlier age at menarche than those who were born from the 1940s to 1980s (P < .0001).

Conclusion

These results could be helpful to health and education professionals who should take into account that because there is currently a widening gap between the physical and psychosocial maturity of girls, they might need special support.

Introduction

Menarche is considered an important indicator of pubertal development in girls. The age that menarche occurs is of clinical, public health, and social importance,1 and it reflects numerous health aspects of a population.2

Age at menarche varies substantially between women across different cultures. Rigorous comparisons between the results of different studies are complicated because of methodological aspects. However, there are at least 2 studies in which authors discussed the published data of menarcheal age in different countries at the end of the past century or in the first 2 years of this century. In both studies it was observed that the earliest age of menarche was 12.0 years and the latest was 16.1 or 16.2 years.3, 4 The age at menarche appeared to be earlier in countries where individuals experience the longest life expectancies, and it was associated with good nutritional conditions.3

Age at menarche in Mexico has been reported in some studies conducted between the 1960s and 1990s. In those studies, the age at menarche varied between 12.06 and 12.92 years in urban areas.5, 6, 7, 8, 9, 10 In Mexico City, one of the cities in which the current study was conducted, the ages varied between 12.30 and 12.92 years.5, 6, 8, 9

Several studies worldwide have shown a secular trend toward a reduction in the age at menarche. However, the magnitude of the trend remains in doubt, because there is no consistency in all studies.11

In Europe, the ages at menarche decreased from 16-17 years in the mid-19th century to 13 years in the mid-20th century.2, 12 Subsequent reports also have indicated that age at menarche declined overall for the most part of the 20th century in several countries such as Canada,11 Spain,13 Korea,14, 15 India,16 Japan,17 Taiwan,18 Russia,19 Turkey,20 and Indonesia.21

Whether the secular trends in age at menarche are continuing or have reached their limit is still a matter of debate.14 According to some authors, this trend tends to slow down or stabilize in developed nations,17, 22 whereas recent studies have shown that menarche is occurring earlier in some countries like China,12 South Korea,15 and Brazil.23 In The Netherlands and in the United States, this trend depends on the race/ethnicity and socioeconomic position of the girls.1, 24

In Mexico, a reduction in the age at menarche from 1978 to 2000 was reported in an indigenous rural community,25 but, as far as we know, no study has been made of possible secular trends in urban nonindigenous populations.

There are 3 methods for obtaining age at menarche: (1) The prospective method, in which premenarcheal girls are followed regularly and asked each time if they have begun to menstruate. Despite its accuracy, it is not easy to carry out longitudinal studies and therefore, most authors use other methods. (2) The status quo method in which a girl (or her parent) is asked whether she has had her first menses and her birth date. (3) The recall or retrospective method in which postmenarcheal women are asking to recall their age at first menses.

The objectives of this study were: (1) To estimate the current age at menarche in 2 urban areas from Mexico, using status quo and retrospective methods; and (2) to analyze secular trends in the age at menarche.

Section snippets

Materials and Methods

The study was approved by the corresponding institutional review board of the Institute of Psychological Research, Universidad Veracruzana.

Current Estimated Age at Menarche

In the Mexico City and Xalapa samples, the distribution of data was normal and the χ2 values indicated a good fit to accept the regression models. Distribution of girls according to age at menarche is summarized in Table 2.

According to these models, in Mexico City the estimated mean age at menarche was 11.40 years (CI, 11.14-11.63) using the status quo method. In the same sample of adolescents, the calculated mean age using the retrospective method was 11.42 years (CI, 11.34-11.50). The 95% CIs

Discussion

The results of this study are consistent with previous reports showing a trend toward younger ages for menarche. The age in Mexico City seems to be considerably earlier than ages reported in previous studies conducted in the 1960s-1990s in the same city that also used the status quo method. Because data analyses of the oldest studies did not contemplate regression models, Malina and colleagues7 reanalyzed the data from these studies to estimate the age at menarche using probit analyses, thus

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    The authors indicate no conflicts of interest.

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