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National Guideline Centre (UK). Non-Alcoholic Fatty Liver Disease: Assessment and Management. London: National Institute for Health and Care Excellence (NICE); 2016 Jul. (NICE Guideline, No. 49.)
14.1. Introduction
Through its very definition, people with NAFLD do not consume alcohol in excessive amounts. However, given that the definition allows people with fatty liver disease to drink alcohol up to the national recommended limits, the regular alcohol consumption of people with NAFLD varies between those completely abstinent from alcohol through to those who drink at the national limits. Given that there are explanations for why alcohol and obesity related to NAFLD might synergise in their deleterious effects on the liver, and also some evidence that alcohol may protect against some of the mechanisms responsible for NAFLD, a review of the evidence examining the relationship between moderate alcohol consumption and NAFLD is warranted. It is clearly important, if evidence exists on which to base firm recommendations, to advise people with NAFLD on whether abstinence from alcohol is indicated or whether it is safe or even beneficial to drink alcohol within the national limits.
14.2. Review question: Should people with NAFLD restrict their consumption of alcohol to below national recommended levels?
For full details see review protocol in Appendix A.
Table 69
PICO characteristics of review question.
14.3. Clinical evidence
Two studies were included in the review;42,66 these are summarised in Table 70 below. Evidence from these studies is summarised in the GRADE clinical evidence profile below (Table 71). See also the study selection flow chart in Appendix E, study evidence tables in Appendix H, forest plots in Appendix K and excluded studies list in Appendix M.
Table 70
Summary of studies included in the review.
Table 71
Clinical evidence profile: Alcohol intake and NAFLD progression/presence.
Both studies were longitudinal in design, with 2 assessments of fatty liver, 1 of which was retrospective,66 and 1 prospective.42 One study used histological diagnosis to monitor fibrosis progression,42 whilst the other study used ultrasound scan to diagnose the presence or absence of fatty liver.66
Alcohol intake was monitored in both using questionnaires to calculate the weekly alcohol consumption. In 1 study more information including heavy alcohol episodes and changes in alcohol consumption was also measured.42
Similar confounding factors were taken into account in both multivariate analysis including age and BMI.
14.4. Economic evidence
No relevant economic evaluations were identified.
See also the economic article selection flow chart in Appendix F.
14.5. Evidence statements
14.5.1. Clinical
- One small cohort study (n=71) with a multivariate analysis, reported high quality evidence of an increased risk of NAFLD progression of fibrosis (OR: 42, 95% CI: 5.39-329.57) for heavy episodic drinking of alcohol in a population of people with NAFLD in Sweden. Conversely 1 large Japanese cohort study (n=5437) with a multivariate analysis reported moderate to very low quality evidence of an increased benefit in male patients who consume light (HR: 0.72, 95% CI: 0.60-0.86) to moderate (HR: 0.80, 95% CI: 0.57-1.00) alcohol for the regression of NAFLD on ultrasonography. The same effect was not demonstrated in females in the population studied (very low quality evidence)
14.5.2. Economic
- No relevant economic evaluations were identified.
14.6. Recommendations and link to evidence
| Recommendation |
|
|---|---|
| Research recommendation |
|
| Relative values of different outcomes | The GDG agreed that progression of NAFLD was the only relevant outcome for this review, as assessed by a variety of methods, that is, liver biopsy (including NAS), MRI or MRS, ultrasound (reporting absence of steatosis only), ELF, transient elastography or NAFLD fibrosis score. |
| Trade-off between clinical benefits and harms | The GDG also discussed the evidence from prospective cohort studies that suggested that the co-existence of obesity and moderate alcohol intake had a super-additive effect on the rates of liver disease incidence, as well as liver-related mortality. The prospective longitudinal study that was included in this review provided evidence that heavy episodic drinking at least once per month (‘binge drinking’) is a strong risk factor for fibrosis progression in adults with NAFLD. Although the GDG felt that the evidence had limitations (see ‘quality of evidence’ below), they concluded that light to moderate alcohol intake (up to 280g ethanol per week) was not associated with increased rates of NAFLD. The GDG considered the evidence that appeared to demonstrate a decreased rate of development of NAFLD in men drinking up to 280g of ethanol per week, but no effect of such levels of consumption on NAFLD rates in women. However, based on the identified evidence, the GDG concluded that whilst alcohol consumption within UK recommended levels appears to be safe in people with NAFLD, the limitations of the evidence meant that they were not able to conclude that alcohol intake beyond current UK limits could be deemed safe or recommendable for people with NAFLD. Given the modest amount of evidence that was identified to inform this review question and its clear major clinical importance, the GDG concluded that a research recommendation was justified for studies to investigate whether people with NAFLD should restrict their alcohol intake to below national recommended levels. |
| Trade-off between net clinical effects and costs | No relevant economic evaluations were identified. The cost of alcoholic drinks falls upon people with NAFLD as consumers. The recommendation in this review would either not affect the quantity of alcoholic drinks consumed or may require advising individuals to reduce their consumption, which would have the additional economic benefit of saving them money. |
| Quality of evidence | The GDG noted that there was high quality evidence reporting a long follow-up of participants (13.8 ± 1.2 years) and careful evaluation of alcohol intake with multivariate analysis adjusting for key confounders. The GDG noted, however, that in their experience, it is unusual for people to begin heavy episodic drinking after the diagnosis of NAFLD and it may indicate that the study participants' original level of alcohol consumption may have been self-reported lower than the true values. Whilst the GDG noted the very large number of participants and long length of follow-up within a large retrospective cohort study, they expressed several concerns regarding risk of bias due to the study design; for instance, the GDG noted that NAFLD had been diagnosed via ultrasound only and that people with heavy alcohol intake were included (who may have had alcohol-related liver disease). In light of this concern, data for participants with heavy alcohol intake were not included within this review. The GDG were also concerned about the indirectness of the prognostic factor measured in the study, which used local recommended alcohol limits in analysing the data that were dissimilar to those in the UK. The GDG were also concerned regarding the analysis of the data and whether it took into account both those who had progressed from baseline and those that had regressed, and noted that this was not clearly reported within the study. The evidence was therefore rated as very low quality due to these risks of bias and indirectness. |
| Other considerations | The GDG were aware of existing evidence (univariate in design) that has shown a correlation between moderate alcohol intake and fibrosis regression in NAFLD cohorts. In addition, they noted data from the cardiovascular literature consistent with moderate alcohol intake being protective against cardiovascular events, a major cause of morbidity and mortality in people with NAFLD. However, they recognised that this evidence could not be used to formulate recommendations for this review question, as the analysis in these studies does not account for key variables that may also influence changes in fibrosis. The GDG discussed that although no specific recommendation on alcohol intake in teenagers with NAFLD could be made, they agreed that teenagers with NAFLD should be given pragmatic advice about alcohol intake and advised of the risks of regular excess alcohol consumption and heavy intermittent drinking, both for their NAFLD and for their health more broadly, recognising UK alcohol licensing laws. Research recommendation The GDG made a research recommendation to investigate if people with NAFLD should restrict their consumption of alcohol to below national limits. See Appendix Q for further details. |
- Alcohol advice - Non-Alcoholic Fatty Liver DiseaseAlcohol advice - Non-Alcoholic Fatty Liver Disease
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