Alcohol Consumption in Patients with Non-alcoholic Fatty Liver Disease: Convenient vs. Inconvenient Truths

Does moderate alcohol consumption accelerate the progression of liver disease in NAFLD? A systematic review and narrative synthesis

OBJECTIVES

Liver disease is a leading cause of premature death, partly driven by the increasing incidence of non-alcohol-related fatty liver disease (NAFLD). Many people with a diagnosis of NAFLD drink moderate amounts of alcohol. There is limited guidance for clinicians looking to advise these patients on the effect this will have on their liver disease progression. This review synthesises the evidence on moderate alcohol consumption and its potential to predict liver disease progression in people with diagnosed NAFLD.

METHODS

A systematic review of longitudinal observational cohort studies was conducted. Databases (Medline, Embase, The Cochrane Library and ClinicalTrials.gov) were searched up to September 2020. Studies were included that reported progression of liver disease in adults with NAFLD, looking at moderate levels of alcohol consumption as the exposure of interest. Risk of bias was assessed using the Quality in Prognostic factor Studies tool.

RESULTS

Of 4578 unique citations, 6 met the inclusion criteria. Pooling of data was not possible due to heterogeneity and studies were analysed using narrative synthesis. Evidence suggested that any level of alcohol consumption is associated with worsening of liver outcomes in NAFLD, even for drinking within recommended limits. Well conducted population based studies estimated up to a doubling of incident liver disease outcomes in patients with NAFLD drinking at moderate levels.

CONCLUSIONS

This review found that any level of alcohol intake in NAFLD may be harmful to liver health.Study heterogeneity in definitions of alcohol exposure as well as in outcomes limited quantitative pooling of results. Use of standardised definitions for exposure and outcomes would support future meta-analysis.Based on this synthesis of the most up to date longitudinal evidence, clinicians seeing patients with NAFLD should currently advise abstinence from alcohol.

PROSPERO REGISTRATION NUMBER

The protocol was registered with PROSPERO (#CRD42020168022).

Light-to-Moderate Alcohol Consumption Is Associated With Increased Risk of Type 2 Diabetes in Individuals With Nonalcoholic Fatty Liver Disease: A Nine-Year Cohort Study

OBJECTIVE

This study explored the association between light-to-moderate alcohol consumption (LMAC) and risk of type 2 diabetes mellitus (T2DM) in individuals with nonalcoholic fatty liver disease (NAFLD).

METHODS

A 9-year cohort study was performed among Chinese men who underwent their annual health checkups between 2009 and 2018. NAFLD was diagnosed based on abdominal ultrasound with exclusion of excess alcohol intake and other causes of liver disease. Logistic regression and Cox proportional regression analyses were applied to identify the risk of prevalent and incident T2DM.

RESULTS

Of the 7,079 participants enrolled, 243 had T2DM at baseline and 630 developed T2DM during the 45,456 person-years follow-up. Both at the baseline and by the end of the follow-up, LMAC was associated with a decreased risk of prevalent T2DM in NAFLD-free participants but with a significantly increased risk in patients with NAFLD. LMAC was also associated with a decreased risk of incident T2DM in NAFLD-free participants. The adjusted hazard ratios (95% confidence interval) of incident T2DM were 0.224 (0.115-0.437) and 0.464 (0.303-0.710) for NAFLD-free light drinkers and NAFLD-free moderate drinkers, respectively. Nondrinking, light-drinking, and moderate-drinking patients with NAFLD all showed significantly increased risks of incident T2DM. Compared with NAFLD-free nondrinkers, the adjusted hazard ratios (95% confidence interval) of incident T2DM were 1.672 (1.336-2.092), 2.642 (1.958-3.565), and 2.687 (2.106-3.427) for nondrinking, light-drinking, and moderate-drinking patients with NAFLD, respectively.

DISCUSSION

LMAC decreased the risks of prevalent and incident T2DM in NAFLD-free participants. LMAC, however, was associated with an increased risk of T2DM in patients with NAFLD (ClinicalTrials.gov number: NCT03847116).