In a recent study published in the journal JAMA Network Open, researchers investigated the association between the consumption of alcohol and the risk of all-cause mortality and the role of bias in influencing the results.
Study: Association Between Daily Alcohol Intake and Risk of All-Cause Mortality. Image Credit: dan.nikonov/Shutterstock.com
The proposition that low levels of alcohol consumption might provide health benefits and protection against all-cause mortality has been highly controversial.
Observational studies and various meta-analyses have reported that individuals who consume moderate amounts of alcohol live longer and have a lower probability of heart disease as compared to individuals who abstain from alcohol consumption.
However, there is evidence that these findings are a result of systematic biases, such as the use of health indicators that are not associated with alcohol consumption, including diet, dental hygiene, income, and weight.
Other biases include the failure to differentiate between complete abstainers and former drinkers and the possibility that abstainers might have poor health from other causes.
Two previous meta-analyses by the same team of researchers found that when potential confounding variables and biases were accounted for, low levels of alcohol consumption were not associated with any reduction in mortality risk.
However, the authors believe that with the emergence of newer, more recent studies, this association needs to be re-investigated.
About the study
In the present study, the researchers conducted a systematic review of studies published until July 2021 and performed a meta-analysis to determine associations between alcohol consumption and the risk of all-cause mortality.
Furthermore, the analysis also investigated the association between all-cause mortality risk and alcohol consumption according to median ages and the sex distribution in the study population.
To minimize the bias associated with lifetime selection, the researchers studied cohorts consisting of individuals recruited before the age of 51 years and followed up till a minimum median age of 60 years.
To eliminate the bias of ill health associated with alcohol abstainers, the analysis included occasional drinkers — individuals that have less than one drink a week — as a comparison.
From the studies included in the systematic review, data comprising alcohol consumption measures, all-cause mortality outcomes, ages of the cohorts during recruitment and follow-up, control variables, and the types of errors involving the misclassification of alcohol abstainers and consumers were extracted for the meta-analysis.
The results reported that low levels of alcohol consumption (less than 25 g per day) were not associated with reductions in all-cause mortality risks for either of the sexes. However, the all-cause mortality risk was significantly higher for females who consumed more than 25 g of alcohol a day and males who drank more than 45 g of alcohol each day.
After accounting for potential biases and confounding effects involving sampling and misclassification of former drinkers, low-volume consumption of alcohol was not found to grant any protective benefits such as a reduced all-cause mortality risk.
The systematic review found that errors involving the misclassification of former or occasional drinkers as abstainers were quite common, with 86 out of the 107 studies having such errors.
The study also found that biases in classifying abstainers and other characteristics of the study altered the relationship between all-cause mortality risk and alcohol consumption, with the controls from most studies attenuating the possible protective effects of alcohol consumption at low volumes or increasing the risks of alcohol consumption.
Furthermore, the use of occasional drinkers as the reference group also resulted in non-significant protective effects of low-volume alcohol consumption as compared to using non-drinkers as the reference group, which reported significant protective effects of low levels of alcohol use.
In the fully adjusted meta-analysis models, not only were the mortality risks higher for individuals who drank more than 45 g of alcohol a day, but for female drinkers, the risk was significantly larger than that for female alcohol abstainers.
To summarize, the researchers investigated the association between low-volume alcohol consumption and reduction in all-cause mortality risk through a systematic review of studies published till July 2021 and a meta-analysis of the data from these studies.
Overall, the findings indicated that when all biases and potential confounders were accounted for, low levels of alcohol consumption did not provide any protective effects against all-cause mortality risk.
Moreover, the results indicated that females who drank more than 25 g of alcohol a day were at a significantly higher mortality risk than female non-drinkers, while for men, the mortality risk increased with alcohol consumption of 45 g a day or more.