Study: Association between alcohol consumption and incidence of dementia in current drinkers: linear and non-linear mendelian randomization analysis. Image Credit: jiris / Shutterstock
In a recent study published in the journal eClinicalMedicine, researchers investigated whether raising the consumption of alcohol causes the risk of developing dementia to increase among individuals who currently drink.
Their findings indicate that predicted alcohol consumption based on genetic factors increases, so does dementia risk, challenging previous knowledge and suggesting that no amount of alcohol is safe when it comes to dementia prevention.
Background
By 2050, the global number of individuals living with dementia is projected to rise to nearly 153 million from over 57 million in 2019, highlighting the urgent need for prevention strategies.
While heavy drinking is a known risk factor for dementia, the effects of consuming light-to-moderate levels of alcohol are still debated. Previous studies are often biased by factors like "abstainer bias," which occurs when people who either quit drinking or choose not to drink due to poor health are compared to drinkers, potentially skewing the results.
These studies may also fail to account for cognitive declines that occur earlier in life or interactions with other health conditions, leading to mixed evidence about whether light-to-moderate alcohol consumption lowers dementia risk.
Past studies have used genetic data to mimic a randomized trial and reduce bias, but these studies assumed a linear relationship. It remains unclear whether light-to-moderate alcohol consumption has a causal impact on dementia risk.
About the study
This study used data from the UK Biobank to find out if drinking light-to-moderate amounts of alcohol causes a higher risk of dementia in people who currently drink alcohol.
First, researchers looked at the relationship between alcohol and dementia using a common statistical method, which allowed them to see if the risk changed at different levels of drinking.
Then, they used a genetic approach called Mendelian Randomization (MR) to see if genes linked to alcohol consumption could help determine if alcohol is directly connected to dementia risk.
The study included over 300,000 white British adults who currently drink alcohol. These participants answered questions about their alcohol habits and provided genetic information. People who did not drink or had dementia at the start of the study were excluded.
Alcohol intake was calculated based on how much people said they drank each week, following UK health guidelines. Dementia cases were tracked through hospital and death records.
The genetic part of the study used information from 95 genes related to alcohol consumption to help figure out if drinking alcohol directly affects dementia risk while adjusting for other factors like age, sex, and lifestyle habits.
Findings
In this study, researchers followed 313,958 current alcohol drinkers for about 13 years to see if their drinking habits were linked to dementia risk. During this time, 1.7% of participants (5,394 people) were diagnosed with dementia.
The average amount of alcohol consumed each week was 13.6 units, with nearly half (48.6%) drinking more than the UK's recommended 14 units per week.
Men generally drank more than women, with men drinking about 20.2 units per week compared to 9.5 units for women. Interestingly, more women (68.6%) stayed within the safe drinking limits compared to men (34.2%).
When analyzing how alcohol consumption is linked to dementia, a "J-shaped" pattern was found.
This means that light-to-moderate drinking (around 11.9 units per week) was associated with the lowest risk of dementia, while higher levels of drinking increased the risk. For men, the lowest dementia risk was at 16.8 units per week, but no clear pattern was found for women.
Genetic analysis showed that people with genes linked to higher alcohol consumption were more likely to develop dementia, especially women. This suggests that alcohol may play a direct role in increasing dementia risk, particularly with heavier drinking.
Conclusions
The study found a linear relationship between the consumption of alcohol and the likelihood of developing dementia, with current drinkers facing higher dementia risk as alcohol intake increased.
This contrasts with conventional epidemiology, which often shows a J-shaped relationship, suggesting moderate drinking might have protective effects.
However, this study's MR analysis suggests these protective effects could be due to biases in traditional studies, such as "abstainer bias" or confounding factors like socioeconomic status.
Strengths include the use of MR to minimize confounding and reverse causality and both linear and non-linear MR analyses to assess alcohol's impact on dementia. The study's limitations include its reliance on self-reported alcohol data, potential bias from selective UK Biobank participants, and the focus on current drinkers, limiting the results' applicability to other groups.
Future research should include diverse populations to better understand alcohol's impact on dementia risk across racial and ethnic groups.
Journal reference:
- Association between alcohol consumption and incidence of dementia in current drinkers: linear and non-linear Mendelian randomization analysis. Zheng, L., Liao, W., Luo, S., Li, B., Liu, D., Yun, Q., Zhao, Z., Zhao, J., Rong, J., Gong, Z., Sha, F., & Tang, J. eClinicalMedicine (2024). DOI: 10.1016/j.eclinm.2024.102810, https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(24)00389-4/fulltext