Dr Erik Skovenborg examines the data on how drinking might influence the development of dementia.
The answer to the question I pose in the title is yes, both—because the status of alcohol as a risk or protective factor depends on your drinking habits. The Whitehall II study began in 1985, investigating social, behavioral, and biological factors in health. A follow-up report began in 2018, studying the link between alcohol and dementia in 9,087 middle-aged men and women. It found the risk of dementia increased in long-term abstainers and those reporting decreased alcohol consumption, compared with long-term consumption of 1–14 standard drinks per week.1 Drinking more than 14 drinks per week increased the risk of dementia, and use of refined categories in the supplementary analyses showed harm to cognitive health in those who drank 36g or more of alcohol every day. A total yes score of 2 or greater on the four CAGE Questions for Alcohol Use (for example, Have you ever had a drink first thing in the morning to steady your nerves or to get rid of a hangover?) was associated with double risk, while alcohol-related hospital admission quadrupled the risk of dementia.
Wine—the milk of old age
The Sephardic scholar Maimonides (1135–1204) praised wine as the milk of old age. In a study of 3,777 residents aged 65+ years from the French departments of Gironde and Dordogne, regular drinking of 3–4 glasses of wine per day was associated with a significantly lower risk of dementia (odds ratio 0.18) and Alzheimer’s disease (odds ratio 0.25), as compared to abstention.2 In the 2018 Whitehall II study, an increased risk of dementia among abstainers was observed only in those who abstained from wine.1 Wine contains polyphenolic compounds, which have been associated with neuroprotective, as well as cardioprotective, effects.
Wine is not, however, the only protective alcoholic beverage. In a study of 1,344 elderly residents from the San Diego suburb of Rancho Bernardo, cognitive function was assessed at four-year intervals between 1988 and 2009 in order to study the association between alcohol intake (beer, wine, and spirits) and living to age 85 without cognitive impairment. Relative to non-drinkers, near-daily drinkers had two- to threefold higher odds of living to at least 85 without cognitive impairment, versus living to at least age 85 with cognitive impairment or death before 85.3
Related
A meta-analysis of individual participant data from 15 prospective cohort studies, from countries situated in six continents, investigated the dementia risk associated with alcohol use in adults aged over 60 years. Mean age at study baseline was 71.8 years (range 60–102 years). Results showed that, when compared with abstainers, the risk for dementia was lower in occasional (hazard ratio [HR] = 0.78), light to moderate (HR = 0.78), and moderate to heavy drinkers (HR = 0.62). In dose–response analyses, moderate drinking of up to 40g alcohol/day was associated with a lower risk of dementia when compared with lifetime abstaining.4
Potential protective mechanisms
Several cardiovascular risk factors are known to be associated with cognitive impairment, and a high hemoglobin A1C level is associated with increasing risk of diabetes and impaired memory function. In the Whitehall II cohort study, part of the excess risk of dementia in abstainers was attributable to a greater risk of cardio-metabolic diseases such as heart attack, stroke, and type 2 diabetes.1 The potential mechanisms underpinning the protective effect of light to moderate alcohol may be related to the reduced risk of cardiovascular disease and type 2 diabetes associated with moderate alcohol consumption.
The glymphatic system is a waste-clearance pathway of the central nervous system that facilitates the flow of cerebrospinal fluid to the venous perivascular spaces, ultimately clearing waste products from the brain. In recent years, findings from rodent studies have suggested that a decreased glymphatic function leads to accumulation in brain tissue of amyloid-beta and tau—the trigger and bullet in development of Alzheimer’s disease.5 Other rodent-study results have suggested that alcohol has a J-shaped effect on the glymphatic system, whereby low doses of ethanol (0.5g/kg) increase glymphatic function following acute exposure, as well as after one month of chronic exposure. Conversely, acute exposure to 1.5g/kg alcohol (binge level) dramatically suppressed glymphatic function in mice, which might contribute to the higher risk of dementia observed in heavy drinkers.6
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More life years without dementia
In a study of 2,449 participants aged 65 years and older in the Chicago Health and Aging Project, Dhana and colleagues combined five lifestyle factors (diet, late-life cognitive activities, physical activities, smoking, and alcohol consumption) in a score ranging from 0 to 5, with higher scores indicating healthier behaviors.7 A light to moderate alcohol consumption (1–15g/day in women and 1–30g/day in men) was considered a healthy factor.
Participants with healthier lifestyles had longer life expectancies. Importantly, however, their extra years of life did not mean extra time living with Alzheimer’s dementia. Life expectancy at 65 was 24.2 years for women with the healthiest lifestyles and 21.1 years for those with the least healthy lifestyles. The former spent 2.6 years (10.8%) of their remaining years with Alzheimer’s dementia, compared with 4.1 years (19.3%) for the latter. Life expectancy at 65 was 23.1 years for men with the healthiest lifestyles, and 17.4 years for those with the least healthy lifestyles. Again, healthier lifestyle was not associated with extra years of dementia: 1.4 years for men in the healthiest lifestyle group versus 2.1 years for men in the least healthy lifestyle group.
Methodological issues
Underreporting: There is most likely some underreporting of alcohol intake in all groups of drinkers and predominantly among heavy drinkers. With a J-curve-association, underreporting lessens the apparent benefit of light to moderate drinking, and studies might overestimate the risk of dementia from a given high level of alcohol intake.
Confounding by lifestyle factors: In the Whitehall II study, abstainers were mainly women, had lower education and physical activity, were obese, and had a higher prevalence of cardio-metabolic risk factors, all associated with an increased risk of dementia, which could explain the differences in risk of dementia. Adjustment for confounding factors did not, however, alter the findings.1
Reverse causation: The concept of reverse causation refers to a process in which the consequence occurs before the cause. For example, impaired smell is one of the earliest features of Alzheimer’s disease; and the loss of smell, or the cognitive decline in itself, could contribute to a loss of interest in wine, causing a reduced intake of wine before the clinical diagnosis of Alzheimer’s. But in the Whitehall II cohort study, the 23-year follow-up included eight assessments of alcohol consumption between 1985/88 and 2015/16. Participants with long-term abstinence had a 74% increased risk of dementia compared to those with long-term consumption of 1–14 drinks per week.1
Conclusion
A Swedish study to examine the associations between different risk factors and future cognitive functions showed education to be the strongest protective predictor. The second-strongest protective factor was alcohol, where consumption in the upper three quartiles—Q2 (0.2–0.5 drinks/day), Q3 (0.6–1.0 drinks/day), and Q4 (≥1.1 drinks/day)—were associated with a better memory and attention/executive function using the lowest consumption quartile, Q1 (< 0.2 standard drinks/day), as the reference. The average intake of alcohol in Quartile 4 was 26.33g, equivalent to 3 UK units.8
“The results presented here permit the conservative message that there is no medical rationale to prevent elderly people to drink a few glasses of wine a day if they like to do so,” Orgogozo and colleagues concluded. “A protective effect against the occurrence of dementia is even suggested by the strong negative correlation observed among the wine drinkers from the Bordeaux area.”2 As a possible protective factor, however, consumption of wine always come with strings attached: a moderate, regular intake of 1–2 drinks most days of the week, preferably with a meal, and ideally combined with a healthy lifestyle.
NOTES
1. S Sabia, A Fayosse, J Dumurgier, A Dugravot, et al, “Alcohol Consumption and Risk of Dementia: 23-year follow-up of Whitehall II cohort study,” British Medical Journal 362 (2018), k2927.
2. JM Orgogozo, F Dartigues, S Lafont,
L Letenneur, et al, “Wine Consumption and Dementia in the Elderly: A prospective community study in the Bordeaux area,” Revue Neurologique 153 (Paris, 1997), pp.185–92.
3. EL Richard, D Kritz-Silverstein, GA Laughlin, TT Fung, et al, “Alcohol Intake and Cognitively Healthy Longevity in Community-Dwelling Adults: The Rancho Bernardo Study,” Journal of Alzheimer’s Disease 59 (2017), pp.803–14.
4. L Mewton, R Visontay, N Hoy, DM Lipnicki, et al, “The Relationship between Alcohol Use and Dementia in Adults Aged More than 60 Years:
A combined analysis of prospective, individual-participant data from 15 international studies,” Addiction 118 (2023), pp.412–24.
5. SY Huang, Y-R Zhang, Y Guo, J Du, et al, “Glymphatic System Dysfunction Predicts Amyloid Deposition, Neurodegeneration, and Clinical Progression in Alzheimer’s Disease,” Alzheimer’s & Dementia 20 (2024), pp.3251–69.
6. I Lundgaard, W Wang, A Eberhardt, HS Vinitsky, et al, “Beneficial Effects of Low Alcohol Exposure, but Adverse Effects of High Alcohol Intake on Glymphatic Function,” Scientific Reports 8 (2018), pp.1–16.
7. K Dhana, OH Franco, E Ritz, et al, “Healthy Lifestyle and Life Expectancy with and without Alzheimer’s Dementia: Population based cohort study,” British Medical Journal 377 (2022): e068390.
8. I Glans, K Nägga, A-M Gustavsson, E Stomrud, et al, “Associations of Modifiable and Non-Modifiable Risk Factors with Cognitive Functions—a prospective, population-based, 17 years follow-up study of 3,229 individuals,” Alzheimer’s Research & Therapy 16 (2024), article 135. ▉
