Body Configuration as a Predictor of Mortality: Comparison of Five Anthropometric Measures in a 12 Year Follow-Up of the Norwegian HUNT 2 Study

BackgroundDistribution of body fat is more important than the amount of fat as a prognostic factor for life expectancy. Despite that, body mass index (BMI) still holds its status as the most used indicator of obesity in clinical work. MethodsWe assessed the association of five different anthropometric measures with mortality in general and cardiovascular disease (CVD) mortality in particular using Cox proportional hazards models. Predictive properties were compared by computing integrated discrimination improvement and net reclassification improvement for two different prediction models. The measures studied were BMI, waist circumference, hip circumference, waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR). The study population was a prospective cohort of 62,223 Norwegians, age 20–79, followed up for mortality from 1995–1997 to the end of 2008 (mean follow-up 12.0 years) in the Nord-Trøndelag Health Study (HUNT 2). ResultsAfter adjusting for age, smoking and physical activity WHR and WHtR were found to be the strongest predictors of death. Hazard ratios (HRs) for CVD mortality per increase in WHR of one standard deviation were 1.23 for men and 1.27 for women. For WHtR, these HRs were 1.24 for men and 1.23 for women. WHR offered the greatest integrated discrimination improvement to the prediction models studied, followed by WHtR and waist circumference. Hip circumference was in strong inverse association with mortality when adjusting for waist circumference. In all analyses, BMI had weaker association with mortality than three of the other four measures studied. ConclusionsOur study adds further knowledge to the evidence that BMI is not the most appropriate measure of obesity in everyday clinical practice. WHR can reliably be measured and is as easy to calculate as BMI and is currently better documented than WHtR. It appears reasonable to recommend WHR as the primary measure of body composition and obesity.

研究背景 体脂分布作为预期寿命的预后因素，其重要性优于体脂总量。尽管如此，身体质量指数（Body Mass Index, BMI）仍是临床工作中应用最为广泛的肥胖评估指标。

研究方法 本研究采用Cox比例风险模型，分析了5种人体测量指标与全因死亡率及心血管疾病（cardiovascular disease, CVD）死亡率的关联。通过计算两种不同预测模型的综合判别改善指数与净重新分类改善指数，对比了各指标的预测性能。本次研究涉及的人体测量指标包括BMI、腰围、臀围、腰臀比（waist-to-hip ratio, WHR）以及腰高比（waist-to-height ratio, WHtR）。研究队列来自北特伦德拉格健康研究（Nord-Trøndelag Health Study, HUNT 2），共纳入62223名年龄在20~79岁之间的挪威受试者，随访时间为1995-1997年至2008年底，平均随访时长为12.0年。

研究结果 在校正年龄、吸烟状况与体力活动水平后，WHR与WHtR被证实为最强的死亡预测因子。每增加1个标准差的WHR，男性CVD死亡率的风险比（Hazard Ratios, HRs）为1.23，女性为1.27；对于WHtR，男性的HR为1.24，女性为1.23。在本次研究的预测模型中，WHR带来的综合判别改善幅度最大，其次为WHtR与腰围。在校正腰围后，臀围与死亡率呈显著负相关。所有分析结果均显示，BMI与死亡率的关联强度弱于其余4项指标中的3项。

研究结论 本研究进一步佐证了BMI并非日常临床实践中最适宜的肥胖评估指标这一结论。WHR测量简便可靠，计算难度与BMI相当，且目前的研究证据较WHtR更为充分。因此，推荐将WHR作为身体成分与肥胖评估的首选指标具有合理性。