Researchers in Finland and Sweden examined the records of 1,409 people whose coffee drinking habits had been recorded when they were at midlife.
Those who drank three to five cups of coffee per day in midlife were much less likely to have developed dementia or Alzheimer's in follow-up checks two decades or more later, the researchers say in the January issue of the Journal of Alzheimer's Disease.
"Given the large amount of coffee consumption globally, the results might have important implications for the prevention of or delaying the onset of dementia/Alzheimer's disease," Miia Kivipelto, a researcher from the University of Kuopio, Finland, and the Karolinska Institutet in Stockholm, Sweden, says in a news release. "The finding needs to be confirmed by other studies, but it opens the possibility that dietary interventions could modify the risk of dementia/AD. [And it] might help in the development of new therapies for these diseases."
Coffee and Dementia
In the study, participants were asked in 1972, 1977, 1982, or 1987, when they were all in midlife (average age 50), how much coffee they drank. Then they were split into three groups: low coffee drinkers (zero to two cups per day), moderate coffee drinkers (three to five cups per day), and high coffee drinkers (more than five cups per day).
Of the participants, 15.9% were low coffee drinkers, 45.6% were moderate coffee drinkers, and 38.5% were high coffee drinkers.
After an average of 21 years, 1,409 people between ages 65 and 79 were re-examined. A total of 61 were classified as having dementia, 48 with Alzheimer's.
The study showed that coffee drinkers at midlife had a lower risk for dementia or Alzheimer's later in life than people who drank little or no coffee at midlife. The lowest risk was found among moderate coffee drinkers. Moderate coffee drinkers had a 65%-70% decreased risk of dementia and a 62%-64% decreased risk of Alzheimer's compared with low coffee drinkers, the researchers write.
At midlife, those who drink the most coffee daily had the highest total cholesterol levels and the highest rate of smoking. At late life, the low coffee drinkers had the highest occurrence of dementia and Alzheimer's and the highest scores on a scale of depression.
"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 in the central nervous system was still unknown, and ... the pathologic processes leading to Alzheimer's disease may start decades before the clinical manifestation of the disease," Kivipelto says.
The researchers say it's not known how coffee would offer protection against dementia, but that coffee drinking also has been associated with a decreased risk of type 2 diabetes, which is a risk factor for dementia. The authors speculate that the effect may have something to do with coffee's antioxidant capacity in the blood.
The study also showed that tea drinking was not associated with a reduced risk of dementia or Alzheimer's disease.