Background

Inequalities in the trajectories of body composition in childhood and adolescence have been infrequently studied. Despite the importance of environmental factors in obesity development, little research has looked at area-level socioeconomic position, independent of family socioeconomic position. We aimed to assess how inequalities in body composition develop with age.

Methods

The Millennium Cohort Study is a longitudinal study of 19 243 families who had a child born between 2000 and 2002 in the UK. Multilevel growth curve models were applied to examine change in fat mass index (FMI), fat free mass index (FFMI; using the Benn index), and fat mass to fat free mass ratio (FM:FFM), measured using Bioelectrical Impedance Analysis, from ages 7 years to 17 years by the Index of Multiple Deprivation (IMD) and household income at baseline.

Findings

Inequalities in FMI and FM:FFM ratio are evident at age 7 years and widen with age. At age 17 years, adolescents in the most disadvantaged IMD group had FMI 0·57 kg/m^B (B=Benn parameter; 95% CI 0·43 to 0·70) higher and FM:FFM ratio 0·037 (95% CI 0·026 to 0·047) higher compared with the most advantaged group. Disadvantaged socioeconomic position is associated with higher FFMI but is reversed in adolescence after adjustment for FMI. Inequalities were greater in girls at age 7 years (mean FMI 0·22 kg/m^B; 95% CI 0·13 to 0·32) compared with boys of the same age (0·05 kg/m^B; –0·04 to 0·15, p=0·3), but widen fastest in boys, especially for FMI, in which there was over an 11 times increase in the inequality from age 7 years of 0·05kg/m^B (95% CI –0·04 to 0·15) to 0·62 kg/m^B at 17 years (0·42 to 0·82). Inequalities for the IMD were similar to income, and persisted at age 17 years independent of family socioeconomic position.

Interpretation

Childhood and adolescence is an important period to address inequalities in body composition, as they emerge and widen. Policies should consider FFM as well as FM, and inequalities in the environment.

Funding

Medical Research Council, Economic and Social Research Council.

中文翻译：

---

地区层面和家庭层面的社会经济地位和身体成分轨迹：英国千年队列研究的纵向分析

 背景

儿童期和青春期身体成分轨迹的不平等很少被研究。尽管环境因素在肥胖发展中很重要，但很少有研究关注独立于家庭社会经济地位的地区社会经济地位。我们的目的是评估身体成分的不平等如何随着年龄的增长而发展。

 方法

千禧年队列研究是一项针对 2000 年至 2002 年间在英国出生的 19 243 个孩子的家庭的纵向研究。应用多级生长曲线模型来检查脂肪质量指数（FMI）、去脂质量指数（FFMI；使用 Benn 指数）和脂肪质量与去脂质量比率（FM：FFM）的变化，使用生物电阻抗分析测量，根据多重剥夺指数 (IMD) 和基线家庭收入，从 7 岁到 17 岁。

 发现

FMI 和 FM:FFM 比率的不平等在 7 岁时就很明显，并随着年龄的增长而扩大。 17 岁时，处境最不利的 IMD 组青少年的 FMI 较高，为 0·57 kg/m ^B （B=Benn 参数；95% CI 0·43 至 0·70），FM:FFM 比率为 0·037 (95%)与最有利组相比，CI 0·026 至 0·047）更高。不利的社会经济地位与较高的 FFMI 相关，但在 FMI 调整后在青春期发生逆转。与同龄男孩^{(0·05 kg/m B ;} –0· 04 至 0·15，p=0·3），但男孩扩大最快，尤其是 FMI，其中从 7 岁起 0·05kg/m ^B的不平等增加了 11 倍以上（95% CI –0·04 至 0·15) 至 0·62 kg/m ^B ，17 岁时（0·42 至 0·82）。 IMD 的不平等与收入相似，并且在 17 岁时持续存在，与家庭社会经济地位无关。

 解释

儿童期和青春期是解决身体成分不平等问题的重要时期，因为这些不平等现象正在出现并扩大。政策应考虑实况调查、FM 以及环境中的不平等。

 资金

医学研究委员会、经济和社会研究委员会。