Abston Eric, Comellas Alejandro, Reed Robert Michael, Kim Victor, Wise Robert A, Brower Roy, Fortis Spyridon, Beichel Reinhard, Bhatt Surya, Zabner Joseph, Newell John, Hoffman Eric A, Eberlein Michael
Department of Medicine, University of Iowa, Iowa City, Iowa, USA.
Division of Pulmonary, Critical Care and Occupational Medicine, University of Iowa, Iowa City, Iowa, USA.
BMJ Open Respir Res. 2017 Oct 13;4(1):e000231. doi: 10.1136/bmjresp-2017-000231. eCollection 2017.
The obesity paradox in chronic obstructive pulmonary disease (COPD), whereby patients with higher body mass index (BMI) fare better, is poorly understood. Higher BMIs are associated with lower lung volumes and greater lung elastic recoil, a key determinant of expiratory airflow. The forced expiratory flow (25-75) (FEF)/forced vital capacity (FVC) ratio reflects effort-independent expiratory airflow in the context of lung volume and could be modulated by BMI.
We analysed data from the COPDGene study, an observational study of 10 192 subjects, with at least a 10 pack-year smoking history. Data were limited to subjects with BMI 20-40 kg/m (n=9222). Subjects were stratified according to forced expiratory volume in 1 s (FEV) (%predicted)-quintiles. In regression analyses and Cox proportional hazard models, we analysed the association between BMI, the FEF/FVC ratio, the imaging phenotype, COPD exacerbations, hospitalisations and death.
There was no correlation between BMI and FEV(%predicted). However, a higher BMI is correlated with a higher FEF/FVC ratio. In CT scans, a higher BMI was associated with less emphysema and less air trapping. In risk-adjusted models, the quintile with the highest FEF/FVC ratio was associated with a 46% lower risk of COPD exacerbations (OR 0.54, p<0.001) and a 40% lower risk of death (HR 0.60, p=0.02), compared with the lowest quintile. BMI was not independently associated with these outcomes.
A higher BMI is associated with lower lung volumes and higher expiratory airflows when normalised for lung volume, as quantified by the FEF/FVC ratio. A higher FEF/FVC ratio is associated with a lower risk of COPD exacerbations and death and might quantify functional aspects of the paradoxical effect of higher BMIs on COPD.
慢性阻塞性肺疾病（COPD）中的肥胖悖论，即体重指数（BMI）较高的患者病情反而较好，目前人们对此了解甚少。较高的BMI与较低的肺容积和更大的肺弹性回缩力相关，而肺弹性回缩力是呼气气流的关键决定因素。用力呼气流量（25-75）（FEF）/用力肺活量（FVC）比值反映了在肺容积背景下与努力无关的呼气气流，并且可能受BMI的调节。
我们分析了COPDGene研究的数据，这是一项对10192名受试者进行的观察性研究，这些受试者至少有10包年的吸烟史。数据仅限于BMI为20-40 kg/m²的受试者（n=9222）。受试者根据1秒用力呼气容积（FEV）（%预计值）分为五分位数。在回归分析和Cox比例风险模型中，我们分析了BMI、FEF/FVC比值、影像表型、COPD急性加重、住院和死亡之间的关联。
BMI与FEV（%预计值）之间无相关性。然而，较高的BMI与较高的FEF/FVC比值相关。在CT扫描中，较高的BMI与较少的肺气肿和较少的气体潴留相关。在风险调整模型中，与最低五分位数相比，FEF/FVC比值最高的五分位数与COPD急性加重风险降低46%（OR 0.54，p<0.001）和死亡风险降低40%（HR 0.60，p=0.02）相关。BMI与这些结局无独立相关性。
较高的BMI与较低的肺容积相关，并且在以FEF/FVC比值量化的肺容积标准化时，呼气气流较高。较高的FEF/FVC比值与较低的COPD急性加重和死亡风险相关，并且可能量化较高BMI对COPD的矛盾效应的功能方面。
