背景:因为人们关心自己相对于同龄人和社会的体重,肥胖不平等在解释肥胖发生率和肥胖对主观幸福感的影响方面发挥作用。虽然肥胖患病率和平均体重指数(BMI)的增加是有据可查的,分布变化和相应的肥胖不平等的测量尚未得到充分探索。
方法:本研究分析了来自国家健康和营养检查调查(NHANES)I(1971-1974)的20至74岁成年人的BMI数据,II(1976-1980),III(1988-1994),和连续的NHANES(1999-2014)。我们应用了测量收入不平等的工具来分析美国成年人BMI分布的跨期变化。使用随机优势检验,我们构建了研究期间累积BMI分布的部分排序.Shapley分解和不平等指数用于量化时间变化的来源和程度,并将不平等分解为考虑年龄的组内和组间成分。性别,和种族。
结果:每个NHANES研究的BMI分布一阶随机支配了1971-1974年至2003-2006年上一波的BMI分布,而最近的比较未能拒绝零假设非优势。Shapley分解分析显示,自1988-1991年以来,BMI分布的水平变化占肥胖患病率增加的大部分。尤其是近年来肥胖率增长放缓,在2007-2010年和2011-2014年期间,再分配部分的贡献显著下降,甚至变为负值.不平等指数始终显示,从1970年代中期到2000年代中期,无论人口亚群如何,肥胖不平等都在恶化。BMI分布的这种不成比例的变化不太可能是美国人口种族组成变化的结果。
结论:我们的研究结果表明,肥胖患病率看似相似的增加可能伴随着非常不同的分布变化模式。我们发现,美国肥胖流行的早期阶段主要是由偏度增加驱动的,而最近的增长是一种全人口的经历,无论人口特征如何。越来越多的病态肥胖在流行的初始阶段当然发挥了重要作用,但最近,BMI分布基本上水平向右移动。
BACKGROUND: Because people care about their weight relative to peers and society, obesity inequality plays a role in explaining obesity incidence and the impacts of being obese on subjective well-being. While the increase in obesity prevalence and mean body mass index (BMI) is well documented, the measurement of distributional changes and corresponding obesity inequality is yet to be fully explored.
METHODS: The present study analyzed BMI data for adults aged 20 to 74 from the National Health and Nutritional Examination Survey (NHANES) I (1971-1974), II (1976-1980), III (1988-1994), and continuous NHANES (1999-2014). We applied tools developed to measure income inequality to analyze the inter-temporal variation in the BMI distribution among US adults. Using stochastic dominance tests, we construct partial orderings on cumulative BMI distributions during the study period. Shapley decompositions and inequality indices are employed to quantify the source and extent of temporal variation and decompose the inequality into within and between-group components considering age, gender, and race.
RESULTS: The BMI distribution of each NHANES study first-order stochastically dominated the BMI distribution of the previous wave from 1971-1974 to 2003-2006, whereas more recent comparisons failed to reject the null hypothesis of non-dominance. The Shapley decomposition analysis revealed that horizontal shifts of BMI distributions accounted for a majority of the increase in obesity prevalence since 1988-1991. Especially in recent years when the rate of obesity growth has slowed down, the contribution of the redistribution component dropped significantly and even became negative between 2007-2010 and 2011-2014. The inequality indexes consistently show a worsening of obesity inequality from the mid-1970s to the mid-2000s regardless of population subgroups, and this disproportionate shift of the BMI distribution is unlikely to be a result of a changing ethnic composition of the US population.
CONCLUSIONS: Our findings demonstrate that seemingly similar increases in obesity prevalence can be accompanied by very different patterns of distribution change. We find that the early phase of the obesity epidemic in the US was largely driven by increasing skewness, whereas more recent growth is a population-wide experience, regardless of demographic characteristics. Increasing morbid obesity certainly played an important role in the initial phase of the epidemic, but more recently the BMI distribution has largely horizontally shifted to the right.