Drinking 2 to 3 units of alcohol every day is linked to a reduced risk of death among people with early stage Alzheimer's disease, finds research published in the online journal BMJ Open.
Moderate drinking has been associated with a lower risk of developing and dying from heart disease and stroke. But alcohol is known to damage brain cells, and given that dementia is a neurodegenerative disorder, drinking might be harmful in those with the condition.
The researchers therefore wanted to find out if the same potentially positive association between alcohol and a reduced risk of cardiovascular death could be applied to 321 people with early stage Alzheimer's disease, defined as a score of 20 or less on the Mini Mental State Exam (MMSE).
The research team analysed data originally collected on 330 people with early stage dementia or Alzheimer's disease and their primary carers from across Denmark as part of the Danish Alzheimer's Intervention Study (DAISY).
DAISY set out to assess the impact of a 12 month programme of psychosocial counselling and support, and tracked progress for three years afterwards, accumulating a considerable amount of data.
This included information on how much alcohol people with early stage dementia or Alzheimer's drank every day. Around one in 10 (8%) drank no alcohol and at the other end of the scale, around one in 20 (4%) drank more than 3 units daily.
Most of the sample (71%) drank 1 or fewer units a day; 17% drank 2-3 units.
During the monitoring period, 53 (16.5%) of those with mild Alzheimer's disease died. Consumption of 2-3 units of alcohol every day was associated with a 77% lowered risk of death compared with a tally of 1 or fewer daily units.
There was no significant difference in death rates among those drinking no alcohol or more than 3 units every day compared with those drinking 1 or fewer daily units.
These results held true after taking account of influential factors: gender, age, other underlying conditions, whether the individual lived alone or with their primary carer, educational attainment, smoking, quality of life, and MMSE result.
The researchers say there could be several explanations for the findings, including that people who drink moderately have a richer social network, which has been linked to improved quality, and possibly length, of life.
Another explanation may lie in the fact that the seemingly protective effect of alcohol may have been caused by reverse causality, whereby those drinking very little alcohol were in the terminal phase of their life, which would have artificially inflated the positive association.
In a bid to correct for this, the researchers re-analysed the data, omitting the first year of monitoring. But this made no difference to the findings.
"The results of our study point towards a potential, positive association of moderate alcohol consumption on mortality in patients with Alzheimer's disease. However, we cannot solely, on the basis of this study, either encourage or advise against moderate alcohol consumption in [these] patients," they caution.
They suggest that further research looking at the impact of alcohol on cognitive decline and disease progression in patients with mild Alzheimer's disease would be particularly informative.
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Berntsen, S., Kragstrup, J., Siersma, V., Waldemar, G., & Waldorff, F. B. (2015). Alcohol consumption and mortality in patients with mild Alzheimer's disease: a prospective cohort study. BMJ Open, 5(12), e007851.