Brettschneider Anna-Kristin, Rosario Angelika Schaffrath, Ellert Ute
Department of Epidemiology and Health Reporting, Robert Koch Institute, General-Pape-Str, 62-66, 12101 Berlin, Germany.
BMC Res Notes. 2011 Oct 17;4:414. doi: 10.1186/1756-0500-4-414.
For practical and financial reasons, self-reported instead of measured height and weight are often used. The aim of this study is to evaluate the validity of self-reports and to identify potential predictors of the validity of body mass index (BMI) derived from self-reported height and weight.
Self-reported and measured data were collected from a sub-sample (3,468 adolescents aged 11-17) from the German Health Interview and Examination Survey for Children and Adolescents (KiGGS). BMI was calculated from both reported and measured values, and these were compared in descriptive analyses. Linear regression models with BMI difference (self-reported minus measured) and logistic regression models with weight status misclassifications as dependent variables were calculated.Height was overestimated by 14- to 17-year-olds. Overall, boys and girls under-reported their weight. On average, BMI values calculated from self-reports were lower than those calculated from measured values. This underestimation of BMI led to a bias in the prevalence rates of under- and overweight which was stronger in girls than in boys. Based on self-reports, the prevalence was 9.7% for underweight and 15.1% for overweight. However, according to measured data the corresponding rates were 7.5% and 17.7%, respectively. Linear regression for BMI difference showed significant differences according to measured weight status: BMI was overestimated by underweight adolescents and underestimated by overweight adolescents. When weight status was excluded from the model, body perception was statistically significant: Adolescents who regarded themselves as 'too fat' underestimated their BMI to a greater extent. Symptoms of a potential eating disorder, sexual maturation, socio-economic status (SES), school type, migration background and parental overweight showed no association with the BMI difference, but parental overweight was a consistent predictor of the misclassification of weight status defined by self-reports.
The present findings demonstrate that the observed discrepancy between self-reported and measured height and weight leads to inaccurate estimates of the prevalence of under- and overweight when based on self-reports. The collection of body perception data and parents' height and weight is therefore recommended in addition to self-reports. Use of a correction formula seems reasonable in order to correct for differences between self-reported and measured data.
出于实际和经济原因，常使用自我报告的身高和体重而非测量值。本研究旨在评估自我报告的有效性，并确定从自我报告的身高和体重得出的体重指数（BMI）有效性的潜在预测因素。
从德国儿童和青少年健康访谈与检查调查（KiGGS）的一个子样本（3468名11 - 17岁青少年）中收集自我报告和测量的数据。根据报告值和测量值计算BMI，并在描述性分析中进行比较。计算以BMI差异（自我报告减去测量值）为因变量的线性回归模型以及以体重状况错误分类为因变量的逻辑回归模型。14至17岁青少年高估了身高。总体而言，男孩和女孩低估了自己的体重。平均而言，根据自我报告计算的BMI值低于根据测量值计算的BMI值。这种对BMI的低估导致了体重过轻和超重患病率估计的偏差，女孩中的偏差比男孩更强。基于自我报告，体重过轻的患病率为9.7%，超重的患病率为15.1%。然而，根据测量数据，相应的比率分别为7.5%和17.7%。BMI差异的线性回归显示，根据测量的体重状况存在显著差异：体重过轻的青少年高估了BMI，超重的青少年低估了BMI。当模型中排除体重状况时，身体认知具有统计学意义：认为自己“太胖”的青少年在更大程度上低估了他们的BMI。潜在饮食失调的症状、性成熟、社会经济地位（SES）、学校类型、移民背景和父母超重与BMI差异无关联，但父母超重是自我报告定义的体重状况错误分类的一致预测因素。
本研究结果表明，自我报告和测量的身高与体重之间观察到的差异导致基于自我报告对体重过轻和超重患病率的估计不准确。因此，除自我报告外，建议收集身体认知数据以及父母的身高和体重。使用校正公式来校正自我报告和测量数据之间的差异似乎是合理的。
