The association between alcohol consumption and all-cause mortality: An umbrella review of systematic reviews using lifetime abstainers or low-volume drinkers as a reference group
Review
Abstract
Background and aims
Systematic reviews of the relationship between alcohol consumption and all-cause mortality have reported different relative risk (RR) curves, possibly due to the choice of reference group. Results have varied from ‘J-shaped’ curves, where low-volume consumption is associated with reduced risk, to monotonically increased risk with increasing consumption.
The researchers summarised the evidence on alcohol consumption and all-cause mortality exclusively from systematic reviews using lifetime abstainers or low-volume/occasional alcohol users as the reference group.
Methods
The researchers conducted a systematic umbrella review of systematic reviews of the relationship between alcohol consumption and all-cause mortality in prospective cohort studies using a reference group of lifetime alcohol abstainers or low-volume/occasional alcohol users.
Several databases (PubMed/Medline/Embase/PsycINFO/Cochrane Library) were searched to March 2022. Reviews were assessed for risk of bias, and those with reference groups containing former alcohol users were excluded.
Results
From 2149 articles retrieved, 25 systematic reviews were identified, and 5 did not include former alcohol users in the reference group.
4 of the 5 included reviews had high risk of bias.
Three reviews reported a J-shaped relationship between alcohol consumption and all-cause mortality with significant decreased risk for low-volume alcohol use (RR range 0.84 to 0.95), while two reviews did not.
The one review at low risk of bias reported monotonically increased risk with greater consumption (RRs = 1.02, 1.13, 1.33 and 1.52 for low-, medium-, high- and higher-volume alcohol use, respectively, compared with occasional alcohol intake).
All five reviews reported significantly increased risk with higher levels of alcohol consumption (RR range 1.28 to 3.70).
Sub-group analyses were reported by sex and age; however, there were evidence gaps for many important factors. Conversely, 17 of 20 excluded systematic reviews reported decreased mortality risk for low-volume alcohol use.
Conclusions
Over 70% of systematic reviews and meta-analyses published to March 2022 of all-cause mortality risk associated with alcohol consumption did not exclude former alcohol users from the reference group and may therefore be biased by the ‘sick-quitter effect’.
Meaning and added value of the study
New research has identified that alcohol may cause more deaths than previously thought, as evidence reviews over the past 30 years may have underestimated the number of deaths caused by alcohol due to an issue called the ‘sick-quitter effect’.
The study adds urgency to the need for governments to do more to highlight the risks linked with alcohol, particularly various types of cancer including liver and breast cancer, and to support policies that put public health before alcohol industry interests.
Study lead, Dr Peter Sarich, said that more than 70% of global systematic reviews on alcohol health harms since 1993 used non-alcohol users as the comparator to people who consume any alcohol, which can cause biased results.
“Many people identified as non-alcohol users in cohort studies are in fact former heavy alcohol users who have incurred health harms which actually caused them to quit consuming alcohol in the first place,” Dr Sarich said, as per Cancer Council NSW.
Dr Peter Sarich, Postdoctoral Research Fellow, Cancer Council NSW
Ms Clare Hughes, Chair of Cancer Council’s national Nutrition, Alcohol and Physical Activity Committee, commented, as per Cancer Council NSW:
This new review strengthens the evidence surrounding the harms of alcohol use and highlights the need for urgent action.
We’d like to see governments invest in a campaign to raise awareness of the long-term health risks associated with alcohol use, and implement policies to address the pricing, availability, and advertising of alcohol, that have been shown to help reduce alcohol use in the community.”
Clare Hughes, Chair, Cancer Council’s national Nutrition, Alcohol and Physical Activity Committee
The sick-quitter effect
The ‘sick quitter effect’ is when people with compromised health due to previous alcohol use behaviours appear in health data as non-alcohol users, when in fact they are ex-alcohol users with health problems due to alcohol use. When a study compares to this group of people, it can falsely make the harms of alcohol consumption appear smaller or non-existent, or even make it seem like consuming small quantities of alcohol protects against harms.
Dr Sarich said that of the 30% of reviews that were not affected by the ‘sick-quitter’ issue, only one was considered a high-quality review, and found that the risk of death increases with increasing alcohol intake, with no evidence of any protective effects for low-level alcohol use. All of the remaining reviews may have understated the health harms of alcohol.
For further reading about the sick-quitter effect
ABC (2024): “The sick quitter effect – when data can be misleading“
Medscape (2023): “The Sick-Quitter Effect: How Alcohol Can Seem Cardioprotective When It Isn’t“
Cancer Council NSW (2019): “The ‘sick-quitter effect’: potential bias in studies on the health effects of alcohol“
