Tracking of BMI z Scores for Severe Obesity
Tracking of BMI z Scores for Severe Obesity
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DOI：
10.1542/peds.2017-1072
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发表时间：
2017-09-01
期刊：
影响因子：
8
通讯作者：
Berenson, Gerald S.
中科院分区：
文献类型：
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作者：
Freedman, David S.;Berenson, Gerald S.
背景：虽然疾病控制中心 (CDC) 生长图表广泛用于儿童肥胖研究，但已知 BMI z 分数在大于第 97 个百分位的值时不准确。 方法：我们使用 Bogalusa 心脏研究中 6994 名儿童的纵向数据，这些儿童经过多次检查来比较 3 个 BMI 指标的跟踪：性别/年龄 z 分数 (BMIz)，BMI 表示为第 95 个百分位的百分比 (% BMIp95)，以及针对非常高的 z 分数压缩进行调整的 BMI z 分数水平（调整后的 z 分数 [BMIaz]）。后两个指标与 BMIz 不同，没有上限。检查之间的平均间隔为2.8年。我们对肥胖或严重肥胖儿童 (% BMIp95 >= 120%) 中的这些指标特别感兴趣。 结果：尽管总体样本中 3 个指标的跟踪几乎没有差异，但在 247 名严重肥胖儿童中，检查之间 BMIz 水平的相关性 (r = 0.46) 明显弱于 BMIaz 和 % BMIp95 的相关性 (r = 0.65 和 0.61)。年龄分层分析表明，BMIz 的弱跟踪在 10 岁之前尤为明显（r = 0.36 vs 0.57 和 0.60）。尽管 BMI 增加超过 5，但几名严重肥胖儿童在两次检查之间仍显示 BMIz 下降。结论：在严重肥胖儿童中，BMIz 的跟踪较弱。这是因为根据 CDC 生长图表将非常高的 BMI 转换为 z 分数时存在限制。与其使用 BMIz，不如表达相对于 CDC 第 95 个百分位数非常高的 BMI 或使用 BMIaz。
BACKGROUND: Although the Centers for Disease Control (CDC) growth charts are widely used in studies of childhood obesity, BMI z scores are known to be inaccurate at values greater than the 97th percentile.METHODS: We used longitudinal data from 6994 children in the Bogalusa Heart Study who were examined multiple times to compare tracking of 3 BMI metrics: BMI-for-sex/age z score (BMIz), BMI expressed as a percentage of the 95th percentile (% BMIp95), and levels of BMI z score that adjust for the compression of very high z scores (adjusted z score [ BMIaz]). The later 2 metrics, unlike BMIz, do not have an upper limit. The mean interval between examinations was 2.8 years. We were particularly interested in these metrics among children with obesity or severe obesity (% BMIp95 >= 120%).RESULTS: Although there was little difference in the tracking of the 3 metrics in the overall sample, among 247 children with severe obesity, the correlation of BMIz levels between examinations (r = 0.46) was substantially weaker than those for BMIaz and % BMIp95 (r = 0.65 and 0.61). Age-stratified analyses indicated that the weak tracking of BMIz was particularly evident before the age of 10 years (r = 0.36 vs 0.57 and 0.60). Several children with severe obesity showed BMIz decreases between examinations despite having BMI increases of over 5.CONCLUSIONS: Among children with severe obesity, the tracking of BMIz is weak. This is because of the constraints in converting very high BMIs into z scores based on the CDC growth charts. Rather than using BMIz, it would be preferable to express very high BMIs relative to the CDC 95th percentile or to use BMIaz.