Spelta Francesco, Fratta Pasini A M, Cazzoletti L, Ferrari M
Section of Internal Medicine, University of Verona, Policlinico G.B. Rossi, P.le Scuro, 10, 37134, Verona, Italy.
Department of Diagnostic and Public Health, University of Verona, Verona, Italy.
Eat Weight Disord. 2018 Feb;23(1):15-22. doi: 10.1007/s40519-017-0456-z. Epub 2017 Nov 6.
The positive association between overweight, obesity, and cardiovascular and all-cause mortality is well established, even though this relation is typically U shaped with an increased risk also in low-weight subjects. However, being overweight or obese has been associated with a better prognosis in subjects suffering from chronic diseases, id est the "obesity paradox". In both community-dwelling and hospitalized patients with COPD, several studies have reported a significant protective effect of obesity on all-cause mortality, indicating that also in obstructive pulmonary diseases, an obesity paradox may be present. Interestingly, the "paradox" is more evident for subjects with severe bronchial obstruction (i.e., a lower FEV1), while in mild-moderate conditions, the weight-related mortality shows a behavior similar to that observed in the general population. Several factors may confound the relation between COPD, obesity and mortality. The lower FEV1 found in obese people may be linked to a restrictive defect rather than to an obstructive one. Due to the modified chest wall mechanical properties-related to increased fat mass-obese COPD patients may present, respect to their lean counterpart, a lower lung hyperinflation which is associated with higher mortality. The traditional classification of COPD attributes to obese "blue bloaters" a low-grade emphysema in opposition to lean "pink puffers"; the fact that emphysema extent is related to mortality may bias the relationship between weight and survival. It is also to underline that the majority of the studies, consider BMI rather than body composition (a better predictor of mortality) when studying the intriguing relation between weight, COPD, and mortality. Reverse bias has also to be taken into account, hypothesizing that an unintentional weight loss may be the deleterious factor related to mortality, rather than considering obesity a protective one. Further prospective studies are needed to shed light on the complexity of this emerging issue.
Level V: Narrative Review.
超重、肥胖与心血管疾病及全因死亡率之间的正相关关系已得到充分证实，尽管这种关系通常呈U形，体重过轻的个体风险也会增加。然而，超重或肥胖与慢性病患者的较好预后相关，即所谓的“肥胖悖论”。在社区居住和住院的慢性阻塞性肺疾病（COPD）患者中，多项研究报告了肥胖对全因死亡率具有显著的保护作用，这表明在阻塞性肺部疾病中也可能存在肥胖悖论。有趣的是，“悖论”在严重支气管阻塞（即较低的第一秒用力呼气容积[FEV1]）的患者中更为明显，而在轻至中度病情中，体重相关死亡率的表现与一般人群中观察到的相似。有几个因素可能会混淆COPD、肥胖与死亡率之间的关系。肥胖者中较低的FEV1可能与限制性缺陷而非阻塞性缺陷有关。由于与脂肪量增加相关的胸壁力学特性改变，肥胖的COPD患者相对于瘦患者可能存在较低的肺过度充气，而这与较高的死亡率相关。COPD的传统分类将肥胖的“蓝肿型”归为低度肺气肿，与瘦的“粉喘型”相对；肺气肿程度与死亡率相关这一事实可能会使体重与生存率之间的关系产生偏差。还需要强调的是，在研究体重、COPD和死亡率之间的复杂关系时，大多数研究考虑的是体重指数（BMI）而非身体成分（对死亡率更好的预测指标）。还必须考虑反向偏差，即假设非故意体重减轻可能是与死亡率相关的有害因素，而不是将肥胖视为保护因素。需要进一步的前瞻性研究来阐明这个新出现问题的复杂性。
V级：叙述性综述。
