Ditch the decaff: only caffeinated coffee is linked to brain benefits.Credit: Matthew Horwood/Getty
We are, as a species, especially fond of caffeine. Tea is the second-most commonly consumed beverage globally, after water, and most adults in the United States begin their day with coffee. And although many people consume caffeine for a jolt of energy, a study published today in JAMA1 suggests that the stimulant also has a longer-term brain benefit: keeping our minds sharp over time.
The study offers what the authors think is the longest-term data to date on the relationship between caffeine consumption and cognition. It found that moderate caffeine intake from coffee and tea was associated with reductions in both dementia risk and the rate of cognitive decline. Specialists praise the study for its size but note that the results should be interpreted with caution.
“This is a well‑conducted study for the type of data available. However, because it uses observational, not experimental, evidence, the findings can only be considered suggestive,” says Naveed Sattar, a cardiometabolic medicine specialist at the University of Glasgow, UK.
More than a quick pick-me-up
Many studies have investigated the link between caffeine and cognition2. But Yu Zhang, an epidemiologist at Harvard University in Cambridge, Massachusetts, and first author of the study, says that previous work followed participants over relatively short periods, whereas dementia builds over many decades.
The science of tea’s mood-altering magic
For its work, Zhang’s group leveraged two decades-long health studies — the Nurses’ Health Study and the Health Professionals Follow-up Study — to track the caffeine-drinking habits of more than 130,000 health-care professionals over 43 years. Participants in these studies documented their diet every few years. They also filled out questionnaires about their cognitive function and took tests that required them to recount strings of words as an objective measure of cognition.
The team found that moderate consumption of caffeine, amounting to 2–3 cups of coffee or 1–2 cups of tea a day, was associated with the greatest reductions in dementia risk and rate of cognitive decline. But lower levels of consumption were also associated with brain benefits.
Contrary to past work3, the association between caffeine intake and cognitive health held even in those who drank large amounts of coffee: dementia risk was 18% lower in people in the highest bracket of caffeine consumption — up to five cups of coffee a day — than in those who drank little or none.