Alcohol Consumption, Brain Amyloid-β Deposition, and Brain Structural Integrity Among Older Adults Free of Dementia

Alcohol Use Disorder and Dementia: A Review

PURPOSE

By 2040, 21.6% of Americans will be over age 65, and the population of those older than age 85 is estimated to reach 14.4 million. Although not causative, older age is a risk factor for dementia: every 5 years beyond age 65, the risk doubles; approximately one-third of those older than age 85 are diagnosed with dementia. As current alcohol consumption among older adults is significantly higher compared to previous generations, a pressing question is whether drinking alcohol increases the risk for Alzheimer's disease or other forms of dementia.

SEARCH METHODS

Databases explored included PubMed, Web of Science, and ScienceDirect. To accomplish this narrative review on the effects of alcohol consumption on dementia risk, the literature covered included clinical diagnoses, epidemiology, neuropsychology, postmortem pathology, neuroimaging and other biomarkers, and translational studies. Searches conducted between January 12 and August 1, 2023, included the following terms and combinations: "aging," "alcoholism," "alcohol use disorder (AUD)," "brain," "CNS," "dementia," "Wernicke," "Korsakoff," "Alzheimer," "vascular," "frontotemporal," "Lewy body," "clinical," "diagnosis," "epidemiology," "pathology," "autopsy," "postmortem," "histology," "cognitive," "motor," "neuropsychological," "magnetic resonance," "imaging," "PET," "ligand," "degeneration," "atrophy," "translational," "rodent," "rat," "mouse," "model," "amyloid," "neurofibrillary tangles," "α-synuclein," or "presenilin." When relevant, "species" (i.e., "humans" or "other animals") was selected as an additional filter. Review articles were avoided when possible.

SEARCH RESULTS

The two terms "alcoholism" and "aging" retrieved about 1,350 papers; adding phrases-for example, "postmortem" or "magnetic resonance"-limited the number to fewer than 100 papers. Using the traditional term, "alcoholism" with "dementia" resulted in 876 citations, but using the currently accepted term "alcohol use disorder (AUD)" with "dementia" produced only 87 papers. Similarly, whereas the terms "Alzheimer's" and "alcoholism" yielded 318 results, "Alzheimer's" and "alcohol use disorder (AUD)" returned only 40 citations. As pertinent postmortem pathology papers were published in the 1950s and recent animal models of Alzheimer's disease were created in the early 2000s, articles referenced span the years 1957 to 2024. In total, more than 5,000 articles were considered; about 400 are herein referenced.

DISCUSSION AND CONCLUSIONS

Chronic alcohol misuse accelerates brain aging and contributes to cognitive impairments, including those in the mnemonic domain. The consensus among studies from multiple disciplines, however, is that alcohol misuse can increase the risk for dementia, but not necessarily Alzheimer's disease. Key issues to consider include the reversibility of brain damage following abstinence from chronic alcohol misuse compared to the degenerative and progressive course of Alzheimer's disease, and the characteristic presence of protein inclusions in the brains of people with Alzheimer's disease, which are absent in the brains of those with AUD.

Alcohol and stress exposure across the lifespan are key risk factors for Alzheimer's Disease and cognitive decline

Alzheimer's Disease and related dementias (ADRD) are an increasing threat to global health initiatives. Efforts to prevent the development of ADRD require understanding behaviors that increase and decrease risk of neurodegeneration and cognitive decline, in addition to uncovering the underlying biological mechanisms behind these effects. Stress exposure and alcohol consumption have both been associated with increased risk for ADRD in human populations. However, our ability to understand causal mechanisms of ADRD requires substantial preclinical research. In this review, we summarize existing human and animal research investigating the connections between lifetime stress and alcohol exposures and ADRD.

Precocious emergence of cognitive and synaptic dysfunction in 3xTg-AD mice exposed prenatally to ethanol

Alzheimer's disease (AD) is the most common cause of dementia, affecting approximately 50 million people worldwide. Early life risk factors for AD, including prenatal exposures, remain underexplored. Exposure of the fetus to alcohol (ethanol) is not uncommon during pregnancy, and may result in physical, behavioral, and cognitive changes that are first detected during childhood but result in lifelong challenges. Whether or not prenatal ethanol exposure may contribute to Alzheimer's disease risk is not yet known. Here we exposed a mouse model of Alzheimer's disease (3xTg-AD), bearing three dementia-associated transgenes, presenilin1 (PS1M146V), human amyloid precursor protein (APPSwe), and human tau (TauP301S), to ethanol on gestational days 13.5-16.5 using an established binge-type maternal ethanol exposure paradigm. We sought to investigate whether prenatal ethanol exposure resulted in a precocious onset or increased severity of AD progression, or both. We found that a brief binge-type gestational exposure to ethanol during a period of peak neuronal migration to the developing cortex resulted in an earlier onset of spatial memory deficits and behavioral inflexibility in the progeny, as assessed by performance on the modified Barnes maze task. The observed cognitive changes coincided with alterations to both GABAergic and glutamatergic synaptic transmission in layer V/VI neurons, diminished GABAergic interneurons, and increased β-amyloid accumulation in the medial prefrontal cortex. These findings provide the first preclinical evidence for prenatal ethanol exposure as a potential factor for modifying the onset of AD-like behavioral dysfunction and set the groundwork for more comprehensive investigations into the underpinnings of AD-like cognitive changes in individuals with fetal alcohol spectrum disorders.

Associations of Alcohol Consumption with Cerebrospinal Fluid Biomarkers of Alzheimer's Disease Pathology in Cognitively Intact Older Adults: The CABLE Study

BACKGROUND

The relationship between alcohol consumption and Alzheimer's disease (AD) pathology is unclear. Amyloid-β (Aβ) and tau biomarkers in cerebrospinal fluid (CSF) have been proven valuable in establishing prognosis in pre-clinical AD.

OBJECTIVE

We sought to examine the associations between alcohol consumption and CSF AD biomarkers in cognitive intact subjects.

METHODS

A total of 806 cognitively intact participants who had measurements of CSF Aβ, pTau, and total Tau proteins and drinking characteristics were included from the Chinese Alzheimer's Biomarker and Lifestyle (CABLE) study. Linear and logistic regression analyses were utilized to explore the associations of alcohol consumption with CSF AD biomarkers. We examined the interaction effects of age, gender, and apolipoprotein epsilon (APOE) ɛ4 status on the relationships between the frequency of drinking and CSF biomarkers.

RESULTS

The multiple linear regression analyses revealed significant differences in CSF AD biomarkers between infrequent drinking (< 1 times/week) and frequent drinking groups (≥1 times/week). Participants in frequent drinking group had higher CSF p-tau/Aβ42 and tTau/Aβ42. Frequent drinking was significantly associated with greater pTau and tTau abnormalities compared to the infrequent drinking group in older (> 65 years) participants.

CONCLUSION

The present study showed significant associations between drinking frequency and CSF AD biomarkers in cognitively intact older adults. Alcohol consumption may have an influence on AD by modulating amyloid deposition and tau phosphorylation in the preclinical stage.

Alcohol use and dementia: new research directions

PURPOSE OF REVIEW

Alcohol is gaining increased recognition as an important risk factor for dementia. This review summarises recent evidence on the relationship between alcohol use and dementia, focusing on studies published from January 2019 to August 2020.

RECENT FINDINGS

Epidemiological data continues to yield results consistent with protective effects of low-to-moderate alcohol consumption for dementia and cognitive function. However, recent literature highlights the methodological limitations of existing observational studies. The effects of chronic, heavy alcohol use are clearer, with excessive consumption causing alcohol-related brain damage. Several pathways to this damage have been suggested, including the neurotoxic effects of thiamine deficiency, ethanol and acetaldehyde.

SUMMARY

Future research would benefit from greater implementation of analytical and design-based approaches to robustly model the alcohol use-dementia relationship in the general population, and should make use of large, consortia-level data. Early intervention to prevent dementia is critical: thiamine substitution has shown potential but requires more research, and psychosocial interventions to treat harmful alcohol use have proven effective. Finally, diagnostic criteria for alcohol-related dementia require formal validation to ensure usefulness in clinical practice.