A daily cup of tea or coffee could offer more than just a comforting start to the day, with new research suggesting a link between regular consumption and a reduced risk of dementia.
A large new study found that those who regularly consume caffeinated versions of these popular hot drinks also exhibit better mental skills compared to individuals who abstain.
The comprehensive research, conducted by experts at Harvard University, analysed data from 131,000 health workers in the US.
These participants, comprising 86,000 female nurses and 45 male health professionals, were tracked for an average of 43 years.
Researchers were also able to identify specific daily consumption levels associated with this decreased dementia risk.
Questionnaires about their diet were completed every two to four years, including questions about caffeinated coffee, decaffeinated coffee and tea consumption.
Cognitive tests were also performed.
During the follow-up period, 11,033 cases of dementia were identified.
Analysis suggested that higher caffeinated coffee intake was significantly associated with lower dementia risk – those who drunk the highest amount of coffee compared to the lowest appeared to have an 18% reduced risk of dementia.
People who drank the most tea appeared to have a 16% reduced risk.
Those who consumed the most tea and coffee also showed a slower rate of cognitive decline compared to those who drank the least.
Among the nurses, higher caffeinated coffee consumption was also associated with better objective cognitive performance.
Higher intake of tea showed similar associations, researchers found.
But drinking decaffeinated coffee was not associated with lower dementia risk or better cognitive performance.
Overall, the authors found that the most “pronounced association” was among people who drank a “moderate” amount of tea or coffee, with “no additional advantages” among people who consumed more.
They estimated that consumption of around two to three cups of caffeinated coffee each day, or one to two cups of tea per day, were linked with the lowest risk of dementia compared to people who did not drink these drinks.
“Greater consumption of caffeinated coffee and tea was associated with lower risk of dementia and modestly better cognitive function, with the most pronounced association at moderate intake levels,” they wrote in Jama.
Lead author, Yu Zhang from the TH Chan School of Public Health at Harvard University, told the Press Association: “Dementia is one of the most important and challenging public health problems worldwide, and there are still very limited effective treatments.
“So identifying modifiable lifestyle factors that may be linked to dementia risk is critical.
“Coffee and tea are widely consumed globally, so even modest associations could have meaningful population-level implications.
“We analysed data from more than 130,000 women and men followed for up to 43 years, with repeated dietary assessments over time.
“We found that higher intake of caffeinated coffee and tea was associated with a lower risk of dementia and better cognitive performance.
“We observed the most favourable associations were at moderate intake levels – the strongest associations were seen at about two to three cups per day of caffeinated coffee and about one to two cups per day of tea.
“We didn’t observe additional benefits at higher intake levels.”
Commenting on the study, Dr Susan Kohlhaas, executive director of research at Alzheimer’s Research UK, said: “This research doesn’t prove that coffee or tea protect the brain.
“This study shows an association, not a cause-and-effect relationship.
“People who drink coffee or tea may also differ in other ways that affect brain health, even after careful adjustment, and the study relied partly on self-reported diagnoses.
“It was also conducted in relatively similar groups of health professionals, which limits how widely the results can be applied.”
Professor Tara Spires-Jones, division lead at the UK Dementia Research Institute, said: “This is a well-conducted study that looked at data from a large number of people over many years.
“However, the study does have important limitations.
“This kind of observational research cannot prove conclusively that caffeine intake was the reason for lower dementia risk, other factors related to coffee and tea-drinking habits could be responsible.
“For example, sleep disruption and several cardiovascular health factors are associated with increased risk of dementia and these can affect people’s choices around caffeine intake.
“Further, the data on caffeine intake were from self-reported questionnaires administered every two to four years, and if people were in early stages of dementia, they might have difficulty accurately reporting their intake or the early brain changes could affect behaviour including caffeine intake.”