The effect of alcohol consumption on cognitive decline is more complicated than we thought. A cohort study published in JAMA Network found that while alcohol intake within the recommended limits may not lower risks of dementia among patients, there was a correlation between infrequent higher-quantity drinking and risk of dementia for people with mild cognitive impairment (MCI). 
The findings were based on the Ginkgo Evaluation of Memory Study, which was originally constituted to study the effectiveness of the dietary supplement Ginkgo biloba in preventing dementia. 3021 participants aged 75 years or older (mean age 78 years, 46.2% female) with normal cognition or MCI, but free of dementia, were chosen for the study. Other influencing factors, such as BMI, blood pressure, tobacco use, and heart conditions were also factored in.
The participants self-reported on their alcohol consumption patterns, specifically drinking frequency and quantity. The researchers found that for those people without MCI, alcohol consumption did not make any difference. However, for participants with MCI, the risk of dementia increased by as much as 72% when the alcohol consumption was equal to or more than 14 drinks per week when compared with individuals who drank less than a drink each week.