Link Between Alcohol Consumption and Multiple Sclerosis: Insights from Mendelian Randomization Studies

Alcohol consumption is a global health concern, linked to numerous diseases. While heavy drinking is universally recognized as harmful, debates persist over the potential health benefits of light-to-moderate alcohol use. Multiple sclerosis (MS), a chronic autoimmune disease of the central nervous system, has been an emerging focus in alcohol research due to its complex interaction with immune and neurological factors. A systematic review of Mendelian Randomization (MR) studies offers new perspectives on alcohol's role in MS and related health outcomes, challenging long-held assumptions about its effects.

Alcohol and Multiple Sclerosis: New Evidence from MR Studies
MS is influenced by both genetic and environmental factors, and alcohol consumption is often considered an environmental risk modifier. Observational studies have suggested conflicting results, with some indicating potential protective effects of moderate drinking against MS. However, MR studies reviewed in this systematic analysis debunked these claims, providing robust evidence of alcohol’s detrimental role:

Increased MS Risk: Genetically predicted alcohol consumption was associated with a significant increase in MS risk. This aligns with growing evidence that alcohol disrupts immune regulation, potentially exacerbating autoimmune disorders.
Cognitive Impact in MS Patients: Beyond MS susceptibility, alcohol consumption was linked to accelerated cognitive decline, a key symptom in MS progression. This finding undermines earlier hypotheses suggesting cognitive benefits of light drinking in MS or other neurological conditions.

Neurological Findings Beyond MS
The review expanded its scope to other neurological disorders, which further contextualize alcohol’s adverse impact:
Epilepsy: A strong causal relationship was identified, highlighting alcohol’s role in increasing seizure risks.
Dementia and Alzheimer’s Disease: Contrary to earlier observational studies suggesting protective effects, MR analyses found no evidence of reduced dementia or Alzheimer’s risk from moderate alcohol intake.

Cardiovascular and Liver Comorbidities in MS Context
Cardiovascular and liver diseases are common comorbidities in MS patients, often influencing disease management and outcomes. The review found:
Cardiovascular Disease: Alcohol consumption was linked to increased risks of hypertension, atrial fibrillation, and myocardial infarction. This is critical for MS patients, who are already predisposed to cardiovascular complications due to reduced mobility and inflammation.
Liver Disease: Alcohol-associated liver damage, including cirrhosis, was confirmed. These findings are relevant for MS management, particularly for patients on disease-modifying therapies metabolized through the liver.

Challenges in the Research
The MR approach offers a more robust method for causal inference than traditional observational studies, but certain limitations persist:
Population Bias: Most studies included in the review were conducted in European populations, limiting the generalizability of findings to non-European ancestries where MS prevalence and alcohol consumption patterns differ.
Instrumental Variables: Genetic variants used as proxies for alcohol consumption could not always differentiate between abstainers, light drinkers, and heavy drinkers, complicating dose-response analyses.

Public Health Implications for MS
The evidence challenges popular misconceptions about the safety of light-to-moderate drinking. For individuals with MS or those at risk, the findings suggest that even low levels of alcohol consumption could contribute to disease onset or exacerbate progression. Public health initiatives must prioritize education on alcohol’s risks and provide tailored guidance for MS patients.

Conclusion
This systematic review underscores alcohol's harmful effects on MS and related health outcomes, dismantling the myth of "safe" consumption levels. It emphasizes the need for cautious alcohol use policies, particularly for populations at risk of or living with MS. Future research should address gaps in non-European populations and explore the interplay between alcohol, genetics, and autoimmune pathways in MS.

References:
Bouajila, N., Domenighetti, C., Aubin, H. J., & Naassila, M. (2024). Alcohol consumption and its association with cancer, cardiovascular, liver and brain diseases: a systematic review of Mendelian randomization studies. Frontiers in epidemiology, 4, 1385064. https://doi.org/10.3389/fepid.2024.1385064