Weng Gong, Dunn Winston
Department of Internal Medicine, The University of Kansas Medical Center, Kansas City, KS, USA.
Transl Gastroenterol Hepatol. 2019 Sep 17;4:70. doi: 10.21037/tgh.2019.09.02. eCollection 2019.
The prevalence of nonalcoholic fatty liver disease (NAFLD) is estimated to be 26.3% among the US population. A subset of this population exhibits an aggressive histological phenotype, nonalcoholic steatohepatitis (NASH) with ≥ stage 2 fibrosis, which may progress to cirrhosis. The definition of NAFLD excludes excessive alcohol intake, which is well known to cause alcoholic liver disease and will not be discussed here. Most NAFLD clinical trials use ~14 drinks per week as the cutoff for excessive alcohol intake. Alcohol consumption below this threshold, which we define as moderate alcohol consumption, is common in the US. According to the 2012 Behavioral Risk Factor Surveillance System (BRFSS), 56% of the US adult population consume alcohol, but only 8.2% report drinking heavily and 18.3% report binge drinking. The American Association for the Study of Liver Diseases (AASLD) Practice Guidance of 2018 states that there are insufficient data to make a recommendation with regard to moderate alcohol consumption in patients with NAFLD, citing a lack of longitudinal studies that examine the impact of moderate alcohol consumption on disease progression and its extrahepatic harms versus benefits, specifically in individuals with established NAFLD. NAFLD prevalence studies have generally noted a negative correlation between modest alcohol consumption and NAFLD. However, prevalence studies have limited application to patients with established NAFLD who present to the clinic. There can also be many confounding factors, because modest alcohol consumption is also negatively associated with some NAFLD risk factors, and those risk factors may not be adequately adjusted for in analyses. The prevalence of NASH with significant fibrosis (≥ F2) is more important because this is the group that is believed to have progressive disease. Thus, cohort studies of disease progression are more important from the patient's standpoint. Because these patients have already developed NAFLD or NASH, their interest lies in their odds of disease progression if they have moderate alcohol consumption compared to abstinence. It is also noteworthy that cardiovascular disease is the most important cause of death among patients with NAFLD. Moderate alcohol consumption has been associated with a reduction in overall mortality, but mostly in cardiovascular mortality. However, this protective effect has not been demonstrated specifically in patients with NAFLD.
据估计，美国人群中非酒精性脂肪性肝病（NAFLD）的患病率为26.3%。该人群中的一部分表现出侵袭性组织学表型，即非酒精性脂肪性肝炎（NASH）且纤维化程度≥2期，这可能会进展为肝硬化。NAFLD的定义排除了过量饮酒，众所周知，过量饮酒会导致酒精性肝病，本文对此不作讨论。大多数NAFLD临床试验将每周饮用约14杯酒作为过量饮酒的临界值。低于此阈值的酒精摄入量，我们定义为适度饮酒，在美国很常见。根据2012年行为风险因素监测系统（BRFSS）的数据，56%的美国成年人口饮酒，但只有8.2%的人报告大量饮酒，18.3%的人报告暴饮。美国肝病研究协会（AASLD）2018年的实践指南指出，关于NAFLD患者适度饮酒，目前没有足够的数据来给出建议，理由是缺乏纵向研究来考察适度饮酒对疾病进展的影响及其肝外危害与益处，特别是在已确诊NAFLD的个体中。NAFLD患病率研究普遍指出适度饮酒与NAFLD之间存在负相关。然而，患病率研究在应用于前来就诊的已确诊NAFLD患者时存在局限性。还可能存在许多混杂因素，因为适度饮酒也与一些NAFLD风险因素呈负相关，而这些风险因素在分析中可能没有得到充分调整。伴有显著纤维化（≥F2）的NASH患病率更为重要，因为这是被认为患有进展性疾病的群体。因此，从患者的角度来看，疾病进展的队列研究更为重要。由于这些患者已经患上了NAFLD或NASH，他们关注的是与戒酒相比，适度饮酒时疾病进展的几率。同样值得注意的是，心血管疾病是NAFLD患者最重要的死亡原因。适度饮酒与总体死亡率降低有关，但主要是心血管死亡率。然而，这种保护作用尚未在NAFLD患者中得到具体证实。
