In a recent study published in Journal of Alcohol and Drug StudiesA gaggle of researchers identified and tested, using theory and evidence, study features that will cause biases in estimates of all-cause mortality risk related to low-alcohol consumption.

Background

A growing body of research challenges the notion that light alcohol consumption protects against serious diseases equivalent to ischemic stroke (a stroke attributable to a blockage in an artery supplying blood to the brain), ischemic heart disease (IHD) (a condition during which narrowed heart arteries reduce blood flow to the guts), and sort 2 diabetes (a chronic condition that affects how the body processes blood sugar). While many observational studies suggest that moderate drinkers live longer and are healthier than abstainers, these comparisons often suffer from selection bias.

Assumptions in regards to the health advantages of alcohol significantly influence global estimates of the burden of disease and national drinking guidelines. Recent analyses have highlighted the critical role of study design, particularly the standards for outlining reference groups, in assessing the health effects of alcohol. High-quality studies are essential to accurately assess the results of sunshine alcohol consumption on mortality. Further research is required to find out the true health effects of sunshine alcohol consumption, free from selection bias and methodological flaws.

Concerning the study

On this study, 107 cohort studies were analyzed to look at the association between alcohol consumption and all-cause mortality risk identified within the systematic review and meta-analysis. Further meta-analyses were conducted in subgroups classified as “lower” or “higher” quality based on potential biases within the reference groups classified as abstainers. The main target was on individuals with low alcohol consumption, defined as one to 2 drinks per day (1.3 g to 24 g ethanol).

In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, studies published as much as July 31, 2021, were identified using Web of Science and PubMed searches and prior meta-analyses. Inclusion criteria were English language, original studies, prospective cohort studies, and general populations. Exclusions included nonoriginal studies and disease-specific participant selection. Data extraction was independently coded by three reviewers, specializing in outcomes, alcohol consumption measures, study characteristics, and controlled covariates.

Potential confounders included contamination of nondrinking reference groups with former or occasional drinkers, baseline disease, cohort median age, controlling for smoking, alcohol measures, and controlling for socioeconomic status (SES). Meta-analytic methods included converting relative risk (RR) estimates to natural logarithm formats, assessing heterogeneity between studies, and conducting mixed-effects regression analyses.

Significant heterogeneity was controlled by inverse variance-weighted mixed regression evaluation. Statistical analyses used SAS version 9.4, and results were converted to exponential scales and significance tests assuming two-sided p values ​​or 95% confidence intervals.

Findings

Studies with younger cohorts, excluding participants with current or previous poor health, assessing alcohol consumption for lower than 30 days, avoiding abstinence bias within the reference group, and never controlling for smoking status or SES showed significantly higher mean RR estimates of all-cause mortality in light drinkers. A complete of 99 studies reported results for light drinkers, with some reporting from multiple cohorts.

Further exploratory evaluation was performed in studies stratified by smoking status due to the significant differences observed. Among the many six studies reporting results for nonsmokers, the RR for light drinkers was 1.16 (95% CI [0.91, 1.41]), in comparison with 0.93 (95% CI [0.71, 1.16]) for the seven studies reporting results for smokers.

Results from the six studies assessed as having a lower risk of lifetime selection bias, defined as no abstinence bias within the reference group and younger cohorts, but not within the older cohorts, showed an RR of 0.98 (95% CI [0.87, 1.11]), near 1.0.

Adjusted RR estimates for light drinkers showed a significantly lower risk of all-cause mortality in your entire pooled set of 107 studies and models meeting combos of lower study quality criteria (older cohorts, misclassification of former and/or occasional drinkers, and poor measurement of alcohol consumption).

Models meeting just one quality criterion (sampling younger cohorts or avoiding abstinence bias) still indicated a lower risk of all-cause mortality (RR = 0.88). Nevertheless, including each quality criteria resulted in an RR of 0.98, which will not be significantly different from 1.0. Adding a higher-quality measure of alcohol increased the RR to a worth above 1.0 (RR = 1.04).

Graphical comparisons of all-cause mortality risk estimates for low-level alcohol consumption revealed significantly lower mortality risks in studies at risk of selection bias, an effect not observed in higher-quality studies. Higher-quality studies meeting all three quality criteria showed higher mortality risks in any respect levels of alcohol consumption compared with lower-quality studies, indicating the importance of rigorous study design in accurately assessing the health effects of low-level alcohol consumption.

Conclusions

In summary, the study analyzed 107 cohort studies of alcohol consumption and all-cause mortality. It found significant heterogeneity supporting the hypothesis of health advantages.

Study characteristics, equivalent to younger cohorts, exclusion of sick participants, and avoidance of abstinence bias, were related to higher RR estimates for light drinkers. Smoking status and SES also influenced the outcomes. High-quality studies didn’t show a big reduction in mortality risk, suggesting that selection bias over the life course creates a spurious health profit for moderate drinking.

The study results underscore the necessity for rigorous research to accurately assess the impact of low-level alcohol consumption on mortality.