Araújo Joana, Barros Henrique, Severo Milton, Lopes Carla, Ramos Elisabete
Department of Clinical Epidemiology, Predictive Medicine and Public Health, University of Porto Medical School, Porto, Portugal Cardiovascular Research and Development Unity, University of Porto Medical School, Porto, Portugal Institute of Public Health, University of Porto, Porto, Portugal.
BMJ Open. 2014 Jun 10;4(6):e004380. doi: 10.1136/bmjopen-2013-004380.
We aimed to assess the trends in body mass index (BMI) and body fat percentage (BF%) from the age of 13 to 17 years and to evaluate how sociodemographic and behavioural characteristics at the age of 13 impact changes in BMI and BF%.
Porto, Portugal.
We evaluated 1451 adolescents in a community-based cohort.
BMI z-scores were calculated according to CDC references. BF% was assessed by bioelectrical impedance. Variables with a significant effect in adiposity changes were identified through linear regression models. In girls, estimates were controlled for duration of follow-up, parental education, baseline BMI z-score, age at menarche and the interaction term baseline BMI z-score×age at menarche; in boys, adjustments were performed for duration of follow-up, parental education, baseline BMI z-score and the interaction term baseline BMI z-score×duration of follow-up.
On average, BMI z-score decreased from the age of 13 to 17 years (mean difference -0.20, 95% CI -0.23 to -0.16 among girls and -0.15, 95% CI -0.19 to -0.11 among boys). Accordingly, 12.4% of girls and 13% of boys moved to a lower BMI category and 2.2% of girls and 5.5% of boys to a higher category. There were sex differences in the significant determinants of adiposity trends. Among girls, BMI z-score significantly decreased with baseline BMI z-score (β=-0.163, 95% CI -0.204 to -0.122) and significantly increased with age at menarche (β=0.078, 95% CI 0.050 to 0.107). Results were similar for BF%. Among boys, BMI z-score significantly increased with higher parental BMI, and BF% decreased among those who wished to look larger at the age of 13 (β=-1.367, 95% CI -2.174 to -0.560), compared with those who were satisfied with their image.
In adolescents, ageing resulted in a decrease in BMI z-scores and BF%. BMI and BF% at the age of 13 were the major determinants of the observed trends. Our results suggest that adolescence is a possible specific time window for intervention.
我们旨在评估13至17岁青少年的体重指数（BMI）和体脂百分比（BF%）的变化趋势，并评估13岁时的社会人口学和行为特征如何影响BMI和BF%的变化。
葡萄牙波尔图。
我们在一个基于社区的队列中评估了1451名青少年。
根据美国疾病控制与预防中心（CDC）的参考标准计算BMI z评分。通过生物电阻抗法评估BF%。通过线性回归模型确定对肥胖变化有显著影响的变量。在女孩中，估计值控制了随访时间、父母教育程度、基线BMI z评分、初潮年龄以及基线BMI z评分×初潮年龄的交互项；在男孩中，对随访时间、父母教育程度、基线BMI z评分以及基线BMI z评分×随访时间的交互项进行了调整。
平均而言，BMI z评分从13岁到17岁有所下降（女孩中的平均差异为-0.20，95%可信区间为-0.23至-0.16；男孩中的平均差异为-0.15，95%可信区间为-0.19至-0.11）。相应地，12.4%的女孩和13%的男孩BMI类别降低，2.2%的女孩和5.5%的男孩BMI类别升高。肥胖趋势的显著决定因素存在性别差异。在女孩中，BMI z评分随基线BMI z评分显著下降（β=-0.163，95%可信区间为-0.204至-0.122），并随初潮年龄显著升高（β=0.078，95%可信区间为0.050至0.107）。BF%的结果类似。在男孩中，父母BMI较高时BMI z评分显著升高，与对自己形象满意的男孩相比，13岁时希望看起来更强壮的男孩BF%降低（β=-1.367，95%可信区间为-2.174至-0.560）。
在青少年中，年龄增长导致BMI z评分和BF%下降。13岁时的BMI和BF%是观察到的趋势的主要决定因素。我们的结果表明，青春期可能是一个特定的干预时间窗口。
