Silva H P, Padez C
Departamento de Antropologia, Museu Nacional, Universidade Federal do Rio de Janeiro, Brazil.
Am J Hum Biol. 2006 Jan;18(1):83-92. doi: 10.1002/ajhb.20458.
The present study is part of a large research project on growth, development, nutrition, and health of Caboclo populations from the Brazilian Amazon. The aim of this paper is to analyze the age of menarche in adolescents (N=164) and adult women (219) in the studied populations. Caboclo are admixed rural, peasant groups that live along the Amazon river and its tributaries, and there are few previous studies about them. Probit analysis of the status quo data yielded a median age at menarche of 12.29+/-1.76 years. The retrospective method was applied to recall data of the 77 post-menarcheal adolescents, yielding an average of 13.06+/-1.27 years. Number of children in the family did not show any statistical influence on age at menarche in any age group. In adult women, age at menarche decreased from 14.50 in those born in 1930 to 12.88 for those born in 1980 (F=4.371, P=0.001). The downward trend found was, on average, 0.237 year per decade in the study period. The median age at menarche in the adolescents (12.29 years) is one of the lowest values found for Central and South American populations. In the ecological context, a low age at menarche could be an adaptive advantage because it provides a greater chance for reproduction at a young age in an environment where, until recently, life expectancy was low. As has been reported for other developing countries, the change found in age at menarche in the women born from the 1930s to the 1980s is likely to be related to changes in health and nutritional factors that occurred in Brazil because this country experienced significant improvement in living standards related to education, vaccination, and health conditions, which, although not equally, reached all regions after the 1960s.
本研究是关于巴西亚马逊地区卡博克洛人群生长、发育、营养与健康的大型研究项目的一部分。本文旨在分析所研究人群中青少年（N = 164）和成年女性（219）的初潮年龄。卡博克洛人是生活在亚马逊河及其支流沿岸的混合农村农民群体，此前关于他们的研究很少。对现状数据进行概率分析得出初潮年龄中位数为12.29±1.76岁。采用回顾性方法回忆77名初潮后青少年的数据，得出平均年龄为13.06±1.27岁。家庭中孩子的数量在任何年龄组对初潮年龄均未显示出统计学影响。在成年女性中，初潮年龄从1930年出生者的14.50岁降至1980年出生者的12.88岁（F = 4.371，P = 0.001）。在研究期间，发现的下降趋势平均每十年为0.237岁。青少年的初潮年龄中位数（12.29岁）是中美洲和南美洲人群中发现的最低值之一。在生态环境中，初潮年龄低可能是一种适应性优势，因为在一个直到最近预期寿命都很低的环境中，它为年轻时繁殖提供了更大机会。正如其他发展中国家所报道的那样，20世纪30年代至80年代出生的女性初潮年龄的变化可能与巴西健康和营养因素的变化有关，因为该国在与教育、疫苗接种和健康状况相关的生活水平方面取得了显著改善，这些改善虽然并不均衡，但在20世纪60年代后覆盖了所有地区。
