Perhaps you're reading this article with a cup of coffee in hand, like 811,300 French people who drink it daily. This puts it ahead of tea, consumed by about two-thirds of the population. It's the second most consumed beverage worldwide after water. And what if, in addition to the little energy boost they provide, caffeinated drinks protected us from dementia? That's what research published in the... Journal of the American Association (Jama).
The link between caffeine consumption and its effects on cognition has been studied for a long time. But until now, it has been impossible to draw clear conclusions. Most studies struggle to differentiate between regular and decaffeinated coffee. This time, some initial trends are beginning to emerge. And this is due to the way the study was designed. The first crucial factor: the participants were followed for an extended period, up to 43 years for some. This is a crucial parameter for identifying gradual cognitive changes as well as the development of dementia over the decades. In addition, the number of participants is particularly high, with 130,000 individuals, which makes the results more reliable. This is the longest and most comprehensive study on the subject to date.
Two to three cups of coffee a day, one to two cups of tea
The results indicate that moderate caffeine consumption—two or three cups of coffee or one or two cups of tea per day—is associated with the greatest reduction in the risk of dementia and cognitive decline (up to 20%). Lower caffeine consumption was also associated with positive brain benefits, but to a lesser extent. And in people who drink large amounts of coffee, up to five cups per day, the risk of dementia was 18% lower than in those who drank little or no coffee.
Caffeine could therefore act on two levels: firstly, on cognitive decline, and then on dementia. Because these are indeed two different concepts. Cognitive decline reflects the early changes in memory and thinking, several years before dementia is diagnosed. Dementia, on the other hand, is a more advanced stage, when impairments become too severe and affect daily life." explains Yuxi Liu, author of the study and researcher at the Harvard University School of Public Health.
Specifically, cognitive decline manifests as a decrease in mental abilities, such as forgetting recent information, disorientation in familiar places, difficulty finding words, or trouble performing familiar tasks. When this decline is established, it is referred to as dementia. Regardless of the stage, caffeine appears to slow the decline in the study participants.
Read alsoNo, coffee cannot completely compensate for your lack of sleep.
Caffeine, stronger than genetics
Even more striking, caffeine consumption appears to override genetic determinism. Indeed, certain genes, such as APOE4, are associated with a much higher risk of cognitive decline. A single copy of this gene in DNA can increase the risk of developing Alzheimer's two to three times. And yet, despite the presence of this gene, caffeine continued to show a protective effect. That's very encouraging", acknowledges Yuxi Liu. This suggests that lifestyle factors can still play a role, even in people with a high genetic risk. This does not mean that genetic risk is eliminated, but rather that several factors are involved.. »
As it stands, it is impossible to conclude that caffeine protects against cognitive decline. Furthermore, researchers have not identified a possible mechanism to explain this association. This is an observational study. We can identify strong associations, but not establish a cause-and-effect relationship.", explains the researcher. This would require conducting a randomized trial or studying more precisely the biological mechanism by which caffeine could protect against dementia.
That said, the researchers have a hunch they're onto something promising. For once, the results clearly differentiate between people who drink regular coffee and those who drink decaffeinated coffee. In the latter group, no cognitive benefits were observed, reinforcing the hypothesis that caffeine does indeed play a role. To delve deeper, the team is now seeking to better understand which biological mechanisms might be linked to caffeine consumption.
At the heart of this research is the gut microbiota, or the collection of organisms present in our intestines. They could play a central role in how caffeine is metabolized. While awaiting answers to these questions, tea and coffee lovers can continue to enjoy their hot beverages, which appear to be a long-term ally.
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