Objective:To study the trend of menarche age in Han and Mongolian women born from 1951 to 2005 in Mongolian region.Methods:A cross-sectional cluster sampling survey method was adopted, From 2003 to 2019, a retrospective survey was carried out in three banners/counties in Tongliao region on the female population of Han and Mongols nationalities aged 16 to 46 and conducted under standardized survey procedures and quality control standards. The basic data of menarche age of women born between 1951 and 2005 were obtained. The changes and rules were analyzed by taking 1 year, 5 years and 10 years as nodes.Results:Totally 46 and conducted under standardized survey procedures and quality control standards 928 pepole (24 450 Han and 22 478 Mongolian) were recruited, the survey response rate was 96.09% (46 928/48 836). In one-year-period analysis, the menarche age gradually decreased from 1951 to 2005. The mean menarche age of Han and Mongolian women changed from (16.22±0.52) years and (15.86±1.24) years in 1951 to (12.37±1.15) years and (12.33±0.98) years in 2005, respectively. The mean menarche age of Han and Mongolian women decreased 3.85 years and 3.54 years. The trend of the mean menarche age's change showed a significant negative correlation with the years (all P<0.000 1). In five-year-period analysis, the mean menarche age of Han and Mongolian women changed from (15.54±1.45) years and (15.53±1.48) years from 1951 to 1955 to (12.41±0.97) years and (12.47±0.96) years from 2001 to 2005, the mean menarche age decreased 3.13 years (3.41 months ahead of schedule every 5 years on average) and 3.06 years (3.34 months ahead of schedule every 5 years on average) in Han and Mongolian women respectively. In ten-year-period analysis, the mean menarche age of Han and Mongolian women changed from (15.79±0.95) years and (15.53±1.33) years from 1951 to 1960 to (12.41±0.97) years and (12.47±0.96) years from 2001 to 2005, the mean menarche age decreased 3.38 years (6.76 months ahead of schedule every 10 years on average) and 3.06 years (6.12 months ahead of schedule every 10 years on average) in Han and Mongolian women respectively. During the 15 years from 1951 to 1965, 1966 to 1970, 1971 to 1990, and 1991 to 2000, they were concentrated at the ages of 15-16, 14-15, 13-14, and 12-13, respectively. The proportion of women at 11 years, 12 years and 13 years menarche age were 26.79% (457/1 706), 73.27% (1 250/1 706), and 92.85% (1 584/1 706) during 2001—2005 in Han women, while the proportion were 23.25% (653/2 809), 62.01% (1 742/2 809), and 90.14% (2 532/2 809) in Mongolian women. Conclusion:The menarche age decreased in Han and Mongolian women from 1951 to 2005, and the ethnic groups tended to be the same. It is recommended to start adolescent education at the age of 8-9 years and pay attention to the changing pattern of early onset of menarche.

Objective:To study the trend of menarche age in Han and Mongolian women born from 1951 to 2005 in Mongolian region.Methods:A cross-sectional cluster sampling survey method was adopted, From 2003 to 2019, a retrospective survey was carried out in three banners/counties in Tongliao region on the female population of Han and Mongols nationalities aged 16 to 46 and conducted under standardized survey procedures and quality control standards. The basic data of menarche age of women born between 1951 and 2005 were obtained. The changes and rules were analyzed by taking 1 year, 5 years and 10 years as nodes.Results:Totally 46 and conducted under standardized survey procedures and quality control standards 928 pepole (24 450 Han and 22 478 Mongolian) were recruited, the survey response rate was 96.09% (46 928/48 836). In one-year-period analysis, the menarche age gradually decreased from 1951 to 2005. The mean menarche age of Han and Mongolian women changed from (16.22±0.52) years and (15.86±1.24) years in 1951 to (12.37±1.15) years and (12.33±0.98) years in 2005, respectively. The mean menarche age of Han and Mongolian women decreased 3.85 years and 3.54 years. The trend of the mean menarche age's change showed a significant negative correlation with the years (all P<0.000 1). In five-year-period analysis, the mean menarche age of Han and Mongolian women changed from (15.54±1.45) years and (15.53±1.48) years from 1951 to 1955 to (12.41±0.97) years and (12.47±0.96) years from 2001 to 2005, the mean menarche age decreased 3.13 years (3.41 months ahead of schedule every 5 years on average) and 3.06 years (3.34 months ahead of schedule every 5 years on average) in Han and Mongolian women respectively. In ten-year-period analysis, the mean menarche age of Han and Mongolian women changed from (15.79±0.95) years and (15.53±1.33) years from 1951 to 1960 to (12.41±0.97) years and (12.47±0.96) years from 2001 to 2005, the mean menarche age decreased 3.38 years (6.76 months ahead of schedule every 10 years on average) and 3.06 years (6.12 months ahead of schedule every 10 years on average) in Han and Mongolian women respectively. During the 15 years from 1951 to 1965, 1966 to 1970, 1971 to 1990, and 1991 to 2000, they were concentrated at the ages of 15-16, 14-15, 13-14, and 12-13, respectively. The proportion of women at 11 years, 12 years and 13 years menarche age were 26.79% (457/1 706), 73.27% (1 250/1 706), and 92.85% (1 584/1 706) during 2001—2005 in Han women, while the proportion were 23.25% (653/2 809), 62.01% (1 742/2 809), and 90.14% (2 532/2 809) in Mongolian women. Conclusion:The menarche age decreased in Han and Mongolian women from 1951 to 2005, and the ethnic groups tended to be the same. It is recommended to start adolescent education at the age of 8-9 years and pay attention to the changing pattern of early onset of menarche.