Association between alcohol consumption and amyotrophic lateral sclerosis: a meta-analysis of five observational studies

Alcohol consumption and its association with cancer, cardiovascular, liver and brain diseases: a systematic review of Mendelian randomization studies

Background

The health effects of alcohol consumption, particularly regarding potential protective benefits of light to moderate intake compared to abstinence, remain a subject of ongoing debate. However, epidemiological studies face limitations due to imprecise exposure measurements and the potential for bias through residual confounding and reverse causation. To address these limitations, we conducted a systematic review of Mendelian Randomization (MR) studies examining the causal relationship between alcohol consumption and cancers, cardiovascular, liver, and neurological diseases.

Methodology

We searched PubMed, ScienceDirect and Embase and Europe PMC up to 05/2024 for MR studies investigating the association of genetically predicted alcohol consumption with cancers, cardiovascular, liver and neurological diseases. We assessed methodological quality based on key elements of the MR design a genetic association studies tool.

Results

We included 70 MR studies that matched our inclusion criteria. Our review showed a significant association of alcohol consumption with multiple cancers such as oral and oropharyngeal, esophageal, colorectal cancers, hepatocellular carcinoma and cutaneous melanoma. While the available studies did not consistently confirm the adverse or protective effects of alcohol on other cancers, such as lung cancer, as suggested by observational studies. Additionally, MR studies confirmed a likely causal effect of alcohol on the risk of hypertension, atrial fibrillation, myocardial infraction and vessels disease. However, there was no evidence to support the protective effects of light to moderate alcohol consumption on cognitive function, Alzheimer's disease, and amyotrophic lateral sclerosis, as reported in observational studies while our review revealed an increased risk of epilepsy and multiple sclerosis. The available studies provided limited results on the link between alcohol consumption and liver disease.

Conclusions

Despite the valuable insights into the causal relationship between alcohol consumption and various health outcomes that MR studies provided, it is worth noting that the inconsistent ability of genetic instrumental variables to distinguish between abstainers, light and moderate drinkers makes it difficult to differentiate between U or J-shaped vs. linear relationships between exposure and outcome. Additional research is necessary to establish formal quality assessment tools for MR studies and to conduct more studies in diverse populations, including non-European ancestries.

Systematic Review Registration

www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021246154, Identifier: PROSPERO (CRD42021246154).

One-carbon metabolism pathway genes and their non-association with the development of amyotrophic lateral sclerosis

Although of unknown etiology, some mechanisms associated with the metabolic cycle of folate are speculated to be related to the genesis of amyotrophic lateral sclerosis (ALS). Thus, the aim of the study was to analyze the role of genetic polymorphisms rs1051266 in SLC19A1 gene and rs1805087 in MTR gene and their associations with ALS development. A case-control study was conducted with 101 individuals with ALS and 119 individuals without diagnosis of neurodegenerative diseases, from the Brazilian central population. The polymorphisms were determined using the polymerase chain reaction-restriction fragment length polymorphism technique. The results showed no statistically significant differences, even when genotypes were analyzed by the dominant, recessive, codominant, and overdominant inheritance models. It was observed a statistical significance relating alcohol consumption with individuals in the case group (p = 0.01). Therefore, the need for more studies to evaluate the influence of genetic variants is highlighted, seeking to provide information on the etiopathogenesis of ALS.

Pre-Morbid Risk Factors for Amyotrophic Lateral Sclerosis: Prospective Cohort Study

AIM

In the absence of effective treatments for amyotrophic lateral sclerosis (ALS), a neurodegenerative disorder with high case fatality, there is a clear need to identify its primary risk factors.

METHODS

UK Biobank is a prospective cohort study in which baseline data were captured between 2006 and 2010 in 502,649 participants aged 37 to 73 years. Follow-up for ALS hospitalisations and death was made via national registries.

RESULTS

Eleven years of event surveillance gave rise to 301 hospitalisations and 279 deaths due to ALS. After adjustment for selected confounding factors, being older (hazard ratio per 10 year increase; 95% confidence interval: 1.92; 1.58, 2.33) and male (1.37; 1.00, 1.87) were associated with elevated rates of hospitalisation for ALS. Similar effects were apparent when death ascribed to the disorder was the outcome of interest. Of the remaining 23 social, biological, and behavioural risk indices, however, there was only a suggestion that taller people experienced an increased risk of hospitalisation (per SD increase: 1.31; 1.09, 1.59).

CONCLUSION

In the present, large-scale study, other than well known associations, we did not find convincing evidence of links with ALS for other risk indices.

The Impact of Lifetime Alcohol and Cigarette Smoking Loads on Amyotrophic Lateral Sclerosis Progression: A Cross-Sectional Study

Background—Amyotrophic lateral sclerosis (ALS) is a devastating and untreatable motor neuron disease; smoking and alcohol drinking may impact its progression rate. Objective—To ascertain the influence of smoking and alcohol consumption on ALS progression rates. Methods—Cross-sectional multicenter study, including 241 consecutive patients (145 males); mean age at onset was 59.9 ± 11.8 years. Cigarette smoking and alcohol consumption data were collected at recruitment through a validated questionnaire. Patients were categorized into three groups according to ΔFS (derived from the ALS Functional Rating Scale-Revised and disease duration from onset): slow (n = 81), intermediate (80), and fast progressors (80). Results—Current smokers accounted for 44 (18.3%) of the participants, former smokers accounted for 10 (4.1%), and non-smokers accounted for 187 (77.6%). The age of ALS onset was lower in current smokers than non-smokers, and the ΔFS was slightly, although not significantly, higher for smokers of >14 cigarettes/day. Current alcohol drinkers accounted for 147 (61.0%) of the participants, former drinkers accounted for 5 (2.1%), and non-drinkers accounted for 89 (36.9%). The log(ΔFS) was weakly correlated only with the duration of alcohol consumption (p = 0.028), but not with the mean number of drinks/day or the drink-years. Conclusions: This cross-sectional multicenter study suggested a possible minor role for smoking in worsening disease progression. A possible interaction with alcohol drinking was suggested.

Role of Alcohol Drinking in Alzheimer's Disease, Parkinson's Disease, and Amyotrophic Lateral Sclerosis

Neurodegenerative diseases, including Alzheimer’s disease (AD), Parkinson’s disease (PD) and amyotrophic lateral sclerosis (ALS), increase as the population ages around the world. Environmental factors also play an important role in most cases. Alcohol consumption exists extensively and it acts as one of the environmental factors that promotes these neurodegenerative diseases. The brain is a major target for the actions of alcohol, and heavy alcohol consumption has long been associated with brain damage. Chronic alcohol intake leads to elevated glutamate-induced excitotoxicity, oxidative stress and permanent neuronal damage associated with malnutrition. The relationship and contributing mechanisms of alcohol with these three diseases are different. Epidemiological studies have reported a reduction in the prevalence of Alzheimer’s disease in individuals who drink low amounts of alcohol; low or moderate concentrations of ethanol protect against β-amyloid (Aβ) toxicity in hippocampal neurons; and excessive amounts of ethanol increase accumulation of Aβ and Tau phosphorylation. Alcohol has been suggested to be either protective of, or not associated with, PD. However, experimental animal studies indicate that chronic heavy alcohol consumption may have dopamine neurotoxic effects through the induction of Cytochrome P450 2E1 (CYP2E1) and an increase in the amount of α-Synuclein (αSYN) relevant to PD. The findings on the association between alcohol consumption and ALS are inconsistent; a recent population-based study suggests that alcohol drinking seems to not influence the risk of developing ALS. Additional research is needed to clarify the potential etiological involvement of alcohol intake in causing or resulting in major neurodegenerative diseases, which will eventually lead to potential therapeutics against these alcoholic neurodegenerative diseases.

Association between alcohol exposure and the risk of amyotrophic lateral sclerosis in the Euro-MOTOR study

OBJECTIVES

Several studies focused on the association between alcohol consumption and amyotrophic lateral sclerosis (ALS), although with inconsistent findings. Antioxidants may play a role since lyophilised red wine was found to prolong SOD1 mice lifespan. The aim of this international population-based case-control study performed in Ireland, The Netherlands and Italy was to assess the role of alcohol, and red wine in particular, in developing ALS.

METHODS

Euro-MOTOR is a case-control study where patients with incident ALS and controls matched for gender, age and area of residency were recruited in a population-based design. Logistic regression models adjusted for sex, age, cohort, education, leisure time physical activity, smoking, heart problems, hypertension, stroke, cholesterol and diabetes were performed.

RESULTS

1557 patients with ALS and 2922 controls were enrolled in the study. Exposure to alcohol drinking was not significantly associated with ALS risk. A stratified analysis of exposure to alcohol by cohort revealed significant ORs in The Netherlands and in Apulia, with opposite directions (respectively 0.68 and 2.38). With regard to red wine consumption, only in Apulia the double-fold increased risk (OR 2.53) remained significant. A decreased risk was found for current alcohol drinkers (OR 0.83), while a significantly increased risk was detected among former drinkers (OR 1.63). Analysis of cumulative exposure to alcohol revealed no significant associations with ALS risk.

CONCLUSION

With few exceptions, no significant association was found between alcohol consumption and ALS. The study of the association between alcohol and ALS requires a thorough exploration, especially considering the role of different type of alcoholic beverages.

Elevated Global DNA Methylation Is Not Exclusive to Amyotrophic Lateral Sclerosis and Is Also Observed in Spinocerebellar Ataxia Types 1 and 2

Adult-onset neurological disorders are caused and influenced by a multitude of different factors, including epigenetic modifications. Here, using an ELISA kit selected upon careful testing, we investigated global 5-methylcytosine (5-mC) levels in sporadic and familial amyotrophic lateral sclerosis (sALS and fALS), spinocerebellar ataxia types 1 and 2 (SCA1 and SCA2), Huntington's disease, Friedreich's ataxia, and myotonic dystrophy type 1. We report a significant elevation in global 5-mC levels of about 2-7% on average for sALS (p < 0.01 [F(1, 243) = 9.159, p = 0.0027]) and various forms of fALS along with SCA1 (p < 0.01 [F(1, 83) = 11.285], p = 0.0012) and SCA2 (p < 0.001 [F(1, 122) = 29.996, p = 0.0001]) when compared to age- and sex-matched healthy controls. C9orf72 expansion carrier ALS patients exhibit the highest global 5-mC levels along with C9orf72 promoter hypermethylation. We failed to measure global 5-hydroxymethylcytosine (5-hmC) levels in blood, probably due to the very low levels of 5-hmC and the limitations of the commercially available ELISA kits. Our results point towards a role for epigenetics modification in ALS, SCA1, and SCA2, and help conclude a dispute on the global 5-mC levels in sALS blood.

Risk factors in Swedish young men for amyotrophic lateral sclerosis in adulthood

Recent research suggests that the incidence of amyotrophic lateral sclerosis (ALS) may be on the rise. Since ALS becomes predominant in later life, most studies on causal factors are conducted in middle-aged or older populations where potentially important influences from early life can usually not be adequately captured. We aimed to investigate predictors in young Swedish men for ALS in adulthood. Therefore, we performed a prospective cohort study of young men (aged 16-25, n = 1,819,817) who enlisted 1968-2005 and took part in comprehensive conscription examinations. Incident cases of ALS (n = 526) during up to 46 years of follow-up were identified in the National Hospital Register and Swedish Cause of Death Register. Those who developed ALS had lower BMI (body mass index) at conscription than their peers (p = 0.03). The risk of ALS during follow-up was calculated with Cox proportional hazards models. No associations were found with physical fitness, erythrocyte sedimentation rate, or non-psychotic mental disorders. Low overall muscle strength compared to high overall muscle strength [hazard ratio (HR) 1.36; 95% confidence interval (CI) 1.01-1.83] and low BMI (a one-unit increase HR 0.96; 95% CI 0.93-0.99) and lower erythrocyte volume fraction (a one-unit increase HR 0.96; 95% CI 0.92-0.998) were the statistically significant predictors for ALS in adjusted models. These findings provide novel epidemiologic evidence of a prospective association between low overall muscle strength and erythrocyte volume fraction in young men and ALS risk.

Neurodegenerative and psychiatric diseases among families with amyotrophic lateral sclerosis

OBJECTIVE

To estimate risks of neurodegenerative and psychiatric diseases among patients with amyotrophic lateral sclerosis (ALS) and their families.

METHODS

We conducted a register-based nested case-control study during 1990-2013 in Sweden to assess whether patients with ALS had higher risks of other neurodegenerative and psychiatric diseases before diagnosis. We included 3,648 patients with ALS and 36,480 age-, sex-, and county of birth-matched population controls. We further conducted a follow-up study of the cases and controls to assess the risks of other neurodegenerative and psychiatric diseases after ALS diagnosis. To assess the potential contribution of familial factors, we conducted similar studies for the relatives of patients with ALS and their controls.

RESULTS

Individuals with previous neurodegenerative or psychiatric diseases had a 49% increased risk of ALS (odds ratio 1.49, 95% confidence interval 1.35-1.66) compared to individuals without these diseases. After diagnosis, patients with ALS had increased risks of other neurodegenerative or psychiatric diseases (hazard ratio 2.90, 95% confidence interval 2.46-3.43) compared to individuals without ALS. The strongest associations were noted for frontotemporal dementia, Parkinson disease, other dementia, Alzheimer disease, neurotic disorders, depression, stress-related disorders, and drug abuse/dependence. First-degree relatives of patients with ALS had higher risk of neurodegenerative diseases, whereas only children of patients with ALS had higher risk of psychiatric disorders, compared to relatives of the controls.

CONCLUSIONS

Familial aggregation of ALS and other neurodegenerative diseases implies a shared etiopathogenesis among all neurodegenerative diseases. The increased risk of psychiatric disorders among patients with ALS and their children might be attributable to nonmotor symptoms of ALS and severe stress response toward the diagnosis.