This study documents differences in childhood IQ trajectories of Guatemala City children, aged 6–15 years and born 1961–1993, according to school attended, height-for-age Z-scores (HAZ) and over time (Flynn effect). IQ data come from the Universidad del Valle de Guatemala Longitudinal Study of Child and Adolescent Development. IQ was measured using standardised tests from the Otis-Lennon Mental Ability Test-series. A multilevel model was developed to describe 60,986 IQ observations (level 1), in 22,724 children (level 2), in five schools representing students of different socioeconomic status (SES) (level 3). Average IQ trajectories differed by school. The difference in average IQ at age 11 years between the students of high and low SES schools was 28.7 points. A one-unit increase in HAZ was associated with a 1.42 (0.72, 2.11) unit higher IQ if HAZ was <0, this association was stronger in public compared to private schools. Conversely, one unit increase in HAZ was only associated with a 0.3 (0.001, 0.5) unit higher IQ if HAZ was ≥0. With each birth year increase, IQ at age 11 years increased by 0.14 (95% CI 0.12, 0.16) units, although this Flynn effect attenuated slightly across adolescence. We found no evidence of secular change in the inequality in IQ trajectories (according to school or HAZ). Shorter children from disadvantaged schools in Guatemala City have lower IQ than their taller and wealthier peers, possibly reflecting the damaging effects of poor early life environments both for linear growth and cognitive development.

中文翻译：

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危地马拉城儿童智商轨迹的差异和长期趋势

本研究根据就读学校、年龄别身高 Z 分数 (HAZ) 和时间推移（弗林效应），记录了 1961 年至 1993 年出生的危地马拉城 6 至 15 岁儿童的儿童智商轨迹差异。智商数据来自危地马拉山谷大学儿童和青少年发展纵向研究。智商是使用奥的斯-列侬心理能力测试系列的标准化测试来测量的。开发了一个多级模型来描述代表不同社会经济地位 (SES) 学生的五所学校的 22,724 名儿童（2 级）的 60,986 个 IQ 观察结果（1 级）（3 级）。平均智商轨迹因学校而异。高SES学校和低SES学校的学生在11岁时的平均智商差异为28.7分。如果 HAZ < 0，HAZ 增加 1 个单位与 IQ 升高 1.42 (0.72, 2.11) 个单位相关，与私立学校相比，这种关联在公立学校更为强烈。相反，如果 HAZ ≥ 0，HAZ 增加 1 个单位仅与 IQ 提高 0.3 (0.001, 0.5) 个单位相关。随着出生年份的增加，11岁时的智商增加了0.14（95% CI 0.12，0.16）单位，尽管这种弗林效应在青春期略有减弱。我们没有发现智商轨迹不平等（根据学校或 HAZ）发生长期变化的证据。危地马拉城贫困学校的矮个子儿童的智商低于高个子和富裕的同龄人，这可能反映了不良的早期生活环境对线性生长和认知发展的破坏性影响。