Three cups of coffee ‘lowers risk’ of dementia by fifth
MELBOURNE: Most people can always find an excuse to put the kettle on and now scientists have identified one more reason to make a brew.
A major study by Harvard University has revealed that drinking three cups of tea or coffee a day appears to lower the risk of dementia, as caffeine can help protect the brain.
Researchers looked at data from 131,000 people in the US, who recorded their intake of caffeinated hot drinks and had their memory and health tracked for four decades.
Having at least two or three cups of coffee per day was linked to an 18 per cent lower risk of dementia, while one to two cups of tea each day cut the risk by 16 per cent, compared with those who had very few hot drinks.
More tea and coffee than this had “no additional advantages”, although it did not do any harm.
Scientists believe that caffeine is “neuroprotective” and may slow the degeneration of brain cells by reducing inflammation and prevent the build-up of toxic proteins linked to dementia.
Coffee and tea also contain polyphenols, chemicals that reduce inflammation and boost heart health by increasing the flow of blood to the brain.
The study found that decaffeinated coffee was not associated with lower dementia risk, suggesting that caffeine itself was key to improving brain health.
Dr Daniel Wang, an assistant professor at Harvard Medical School and the study’s senior author, said that encouraging coffee and tea consumption “can be one piece of the puzzle” in terms of preventing dementia.
He added: “When searching for possible dementia prevention tools, we thought something as prevalent as coffee may be a promising dietary intervention.
“While our results are encouraging, it’s important to remember that the effect size is small and there are lots of important ways to protect cognitive function as we age.”
Yu Zhang, another lead author, said: “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.”
The study, published in the journal Jama, involved 131,000 health workers in the US who completed questionnaires about their diet every two to four years and did cognitive tests. During a follow-up period averaging 43 years, 11,033 cases of dementia were identified.
The research is observational and therefore cannot prove cause and effect — other factors, such as people who drink coffee being healthier in general, could also explain the results.
Professor Tara Spires-Jones of the UK Dementia Research Institute said the 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.”
Dr Susan Kohlhaas, director at Alzheimer’s Research UK, said: “This long-running study suggests that people who regularly drank moderate amounts of coffee or tea were less likely to develop dementia later in life. The lowest dementia risk was seen in people drinking around two to three cups of coffee or one to two cups of tea a day. This level of caffeine intake also linked to slightly better scores on memory and thinking tests, although the differences were small.
“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.
“There’s no single food or drink that can prevent dementia. Funding more research will be key to understanding what really reduces risk and how dementia develops over time.”