| Sumario: | This study aims to describe the time trend of age at menarche in Brazilian schoolgirls evaluated in 2007, 2012/2013 and 2018/2019, and to assess its association with having overweight, including obesity and socio‐economic conditions. Three cross‐sectional studies were carried out in 2007, 2012/2013 and 2018/2019 in schoolchildren enrolled between the second and ninth years of elementary school and comprising 838, 688 and 326 schoolgirls, respectively. Body mass index Z scores were calculated and categorised as either without overweight or with overweight (including obesity). The type of school (a proxy of socio‐economic condition) was categorised as either public or private. Menarche data were collected using the status quo and recall methods. The mean age at menarche was estimated by survival analysis. Differences in age at menarche according to the year of survey, weight status and type of school were verified by the Log‐Rank test and Cox's univariate and multiple regression. There was an increase in the prevalence of overweight in girls throughout the surveys, with 21.4% in 2007, 27.2% in 2012 and 28.5% in 2018 (p = 0.007) having overweight. There was a decrease in the mean age at menarche between 2007 and 2018/2019 (12.3 vs. 11.9 years, respectively). The mean age at menarche in girls with overweight was lower in the three time periods when compared to girls without overweight (11.9, 11.8 and 11.5 vs. 12.4, 12.4 and 12.1, respectively). Girls with overweight were more likely to have had earlier age at menarche than girls without overweight (Hazard Ratio 1.57; 95% CI 1.36; 1.80). There were no differences in the age at menarche according to the type of school. The increase in the prevalence of girls with overweight (including obesity) may be associated with the age at menarche. Girls with overweight had a higher risk of earlier age at menarche than girls without overweight.
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