A decreased B2 average years is actually 8
In the 2020, a systematic opinion and you can meta-research proposed your definition of sexual precocity is going to be re-tested having sexual development in improve around the world and you can current into the in the least particular nations (5)
More substantial amount of girls have been examined during the urban than in outlying components, as well as 2 education claimed the fresh new average age of B2 in both metropolitan and rural components (12, 25). 26 age from inside the girls away from towns, and you may ages regarding rural components. This feedback contained a whole lot more single-center training than simply multicenter degree. The biggest level of solitary-cardiovascular system and you may multicenter communities was in fact off Beijing and 9 towns, plus the reasonable average age B2 away from single-cardiovascular system and you will multicenter degree are 8.twenty-six and you can nine.18 many years, respectively.
All of the knowledge included fat and obese girls, and just one article conducted this new probabilistic regression from nipple stage getting fat and you may obese girls (12).
4 Discussion
To the good our training, this is basically the basic logical investigations out of secular style to your timing away from pubertal beginning certainly one of Chinese girls according to age nipple development. An important shopping for of this systematic feedback is the fact that the pubertal nipple development age Chinese girls generally seems to establish an advanced development over the past 2 decades.
It is worth noting that we here observed a trend of early breast development in Chinese girls at both median age and Pstep three and Pten of B2. The median age of B2 advanced by 1.52 years from 1990s to 2010s (9.78 years in 1993 versus 8.26 years in 2010). P3 and P10 for B2 ranged from 7.1-7.95 years in 1993 to 5.86-6.6 years in 2010, which advanced by 1.24 and 1.35 years, respectively. Weighted analyses over the same period showed that P3 and P10 of B2 decreased significantly over time. Studies from many other countries have found that age at thelarche onset was advanced. The Pediatric Research in the US Office Setting (PROS) indicated that the timing of breast development in white American girls was advanced from 10.6 years in 1930s-1940s to 9.96 years in 1992-1993 (26). Another finding revealed that the age of B2 among girls in Den, nearly a year earlier than the years reported in 1992-1993 (27). Atay and colleagues analyzed the median age of breast development in 4,868 healthy girls aged 6-18 years in Turkey in 2009 and compared to data from 40 years ago, and they also observed a downward trend in the median age of breast development (28). Improvement in the socioeconomic and nutritional status ent (12). The present review showed that more studies on breast development of girls in the south than in the north of China, and the timing of breast development differed between the two regions. The lowest B2 median, P10, and P3 ages were 8.26, 6.6, and 5.94 years in southern regions, earlier than 9.5, 7.9, and 7.3 years in northern regions. This phenomenon may be attributable to the differences in economic development, living environment, atmospheric environment, and dietary habits between the north and south of China (18). Also, we observed that breast development of urban girls (8.26 years) began earlier than that of rural girls ( years). This observation might be related to the differences in nutritional status, food composition, or dietary intake of nutrients among urban and rural girls (29, 30). For example, total fat and protein intake, which are relatively higher in urban girls than in rural girls, contribute to earlier adolescence (31).
Presently, China has adopted the common international standard to determine precocious puberty, which is defined as presenting secondary sexual characteristics before age of 8 years (32). This definition originated from Europe and has been used for decades, and it includes 99% of the population with normal pubertal development and 1% of the population with abnormalities (33). However, based on this criterion, some single-center studies have shown that the prevalence of precocious puberty in Chinese girls is much higher than 1%. For example, a survey on the development of pubertal sexual characteristics in >10,000 pri reported that the prevalence of precocious puberty in girls aged 6-7 years was 19% (34). Another survey in 2018 on the adolescent sexual development of >10,000 children aged 6-16 years in Shenzhen also reported that the proportion of girls with secondary sexual characteristics before age of 8 years was % (35). The high prevalence in above surveys collectively suggests that the standard definition of precocious puberty is inappropriate for the current situation of pubertal development of Chinese girls. The results of the Chinese Student Physical Fitness and Health Survey conducted every 5 years showed that the height of 18-year-old girls (near adult height) was still increasing steadily (36), indicating that although pubertal development advanced gradually, its duration did not shorten and adult height remained unaffected. This finding was further confirmed by a longitudinal study from Thailand, which indicated that the final average height of 104 girls age at thelarche of 7-9 years was similar to the average target height (154.0 ± 4.9 cm vs. 153.1 ± 4.8 cm) (37). The results of the above studies further revealed that it is normal for girls to develop early puberty. Although there is a lack of representative investigations on children’s pubertal development, the results of existing multicenter studies showed that B2 of Chinese girls were advanced at both median age and percentile ages. In a newly published multicenter large sample survey, the P3 age of B2 is 6.3 years, further confirming that pubertal onset age of Chinese girls has been significantly ahead of time.
