A few eternal questions:
– Is caffeine good for the brain?
– Does it boost cognitive functions?
– Does it protect against dementia?
There is little doubt that drinking that morning cup of coffee will likely increase alertness, but the main questions that research is trying to answer go beyond that. Basically: is there a sustained, lifetime, benefit or harm from drinking coffee regularly?
The answer, so far, contains good news and bad news. The good news for coffee drinkers is that most of the long-term results are directionally more positive than negative, so no clear harm seems to occur. The bad news is that it is not clear so far whether caffeine has beneficial effects on general brain functions, either short-term or long-term (aged-related decline or risks of dementia).
It is important to note that many of the studies showing an effect of coffee consumption on brain functions or risks of dementia report a correlation or association (they are not randomized clinical trials). As you know, correlation doesn’t prove causation: coffee drinkers may seem to do well in a number in these long-term studies, but there may be other reasons why coffee drinkers do better.
Q: How does caffeine affect my brain?
A: Caffeine is a stimulant.
It belongs to a chemical group called xanthine. Adenosine is a naturally occurring xanthine in the brain that slows down the activity of brain cells (neurons). To a neuron, caffeine looks like adenosine. It is therefore used by some neurons in place of adenosine. The result is that these neurons speed up instead of slowing down.
This increased neuronal activity triggers the release of the adrenaline hormone, which will affect your body in several ways: your heartbeat increases, your blood pressure rises, your breathing tubes open up, sugar is released in the bloodstream for extra energy.
In moderate doses (a few cups a day) caffeine can increase alertness but also reduce fine motor coordination, cause insomnia, cause headaches and nervousness.
Q: Does caffeine boost brain functions?
A: To date 3 studies suggest that the answer is “maybe”.
In one study of over 7000 people, results showed a correlation between current caffeine intake and better performance on 4 tests. This was more pronounced in older individuals than in younger ones (Martin, 1993).
Another study showed that in 1500 people over 65, life-time consumption of coffee was associated with increased performance in 6 out 12 tests. Current intake was related to better performance in only 2 out 12 tests (Johnson-Kozlow, et al., 2002).
The third study showed for a group of 1875 adults aged 24 to 81, current intake of coffee was associated with better performance in 2 tests but not in 4 others. (Hameleers et al., 2000)
Thus, caffeine consumption may be associated with better performance but 1) there are only very few studies so far, 2) this effect seems limited to some tasks only.
Q: Does caffeine protect against age-related cognitive decline?
A: Two studies say “yes” and 3 studies say “no”.
Van Gelder et al. (2007) followed 676 elderly men over 10 years and found that those who drank more coffee showed less decline in the Mini-Mental Test. The least decline was observed with 3 cups a day.
Ritchie et al. (2007) showed that over 4 years, women over 65 (but not men) who drank more than 3 cups a day showed less decline than women who drank one cup or less. This was observed only in a task of verbal memory.
Van Boxtel et al. (2003) followed 1376 individuals aged 24 to 81 for 6 years and found that caffeine intake had a very small impact on a motor task but no effect on verbal memory tasks.
Hameleers et al. (2000) found no evidence that caffeine intake counteracts cognitive age-related decline in a group of 1875 people aged 24 to 81.
The most recent study of 2606 people showed that over 28 years coffee drinking was not related to better performance (Laitala et al., 2009).
As you can see results are mixed. The evidence showing that caffeine reduces age-related cognitive decline is limited: very few studies and very few tasks.
Q: Does caffeine protect against dementia?
A: Three studies say “yes” and 2 studies say “no”.
Maia et al. (2002) studied 54 Alzheimer’s patients and their non-affected relatives (Controls): Higher daily caffeine intake during the 20 years prior diagnosis was found to be associated with lower risk of Alzheimer’s Disease, suggesting that coffee may be protective.
Eskelinen et al. (2009) followed 1409 individuals aged 65 to 79 for 21 years and found that those who drank coffee had less risk of developing dementia than those who didn’t. The lowest risk was in people drinking 3–5 cups a day.
Lindsay et al (2002) studied 4615 individuals over 5 years and found that coffee consumption was associated with a reduced risk of Alzheimer’s Disease.
Ritchie et al. (2007) studied 7017 individuals aged 65 and over and showed that, over 4 years, caffeine consumption did not reduce dementia risk.
The most recent study to date showed that over 28 years, coffee drinking did not affect the risk of mild cognitive impairment or dementia (Laitala et al., 2009).
Here again the evidence is mixed. Based on the few studies, it is not possible at this time to say that coffee consumption indeed decreases the risks of dementia.