The findings came from the Finnish Cardiovascular Risk Factors, Aging and Dementia (CAIDE) Study, conducted by researchers at the University of Kuopio, Finland and the Karolinska Institutet, Stockholm, Sweden, and the National Public Health Institute, Helsinki, Finland. It is published in the January 2009 issue of the Journal of Alzheimer's Disease, currently in press, although abstracts can be viewed online.
The participants of the study included survivors from other research programs, such as the North Karelia Project and the FINMONICA study in 1972, 1977, 1982 and 1987. After the midlife examination, the average follow up was 21 years, and a total of 1,409 participants, aged between 65 and 79 years, completed the project and undertook the end of follow up re-examination in 1998, when 61 of them were diagnosed with dementia, including 48 with Alzheimer's Disease (AD).
At the midlife examination, participants filled in questionnaires that asked them, among other things, how much coffee and tea they drank, and how often.
For this study, the researchers categorized coffee consumption into three bands: low (0-2 cups a day), moderate (3 to 5 cups) and high (over 5 cups a day). Tea drinking was categorized only into two bands: tea drinking and no tea drinking.
Lead researcher Miia Kivipelto, who is an associate professor at the University of Kuopio, Finland and the Karolinska Institutet, Sweden, explained why they did the study:
"We aimed to study the association between coffee and tea consumption at midlife and dementia/AD risk in late-life, because the long-term impact of caffeine on the central nervous system was still unknown, and as the pathologic processes leading to Alzheimer's disease may start decades before the clinical manifestation of the disease."
The results showed that:
- Those who drank coffee in midlife had a lower risk of developing dememtia and AD later in life than those who drank little or no coffee.
- The lowest risk (65 per cent lower risk) was among those who drank moderate amounts of coffee in midlife (3 to 5 cups a day).
- Removing the effect of potential confounders did not change the figures significantly.
- Tea drinking was relatively uncommon and no links were found between this and dementia/AD.
"Given the large amount of coffee consumption globally, the results might have important implications for the prevention of or delaying the onset of dementia/AD. "
The researchers said the findings need to be confirmed by other studies, but nevertheless they highlight the possibility that diet can change a person's risk of late-life dementia or AD.
If, following confirmation of these findings by further research, scientists also discover the mechanisms by which coffee protects against dementia and AD, then it may also be possible to develop new therapies for these conditions, said Kivipelto.
Related reading: Drinking Coffee: More Good Than Harm? (9 July 2012).