A daily cup of coffee or tea could offer more than just comfort, it might also help keep the mind sharp in later life.

New research published in the Journal of Alzheimer’s Disease has linked moderate coffee intake and both moderate and high tea consumption to slower rates of cognitive decline in older adults. The findings come from a long-term analysis of 8,715 dementia-free participants aged 60-85, drawn from the UK Biobank, and tracked over an average of nine years.

What the researchers found

At the start of the study, participants reported their coffee and tea drinking habits, which researchers categorised as never drinkers, moderate drinkers consuming one to three cups per day, or high drinkers consuming four or more cups daily. Cognitive performance was measured in four areas, including fluid intelligence – the ability to solve unfamiliar problems – and memory accuracy.

The analysis revealed that moderate coffee drinkers and those who never drank coffee experienced a slower decline in fluid intelligence and a smaller increase in memory errors compared with high coffee drinkers.

Tea showed a similar trend, with both moderate and high tea drinkers experiencing less decline in fluid intelligence than those who never drank tea. Neither beverage appeared to have a significant effect on reaction time or numeric memory.

Why coffee and tea might help

Coffee and tea contain compounds such as caffeine, polyphenols and flavonoids, which have been linked to anti-inflammatory and antioxidant effects in the brain.

Caffeine has been shown in laboratory studies to influence the development of proteins associated with Alzheimer’s disease, reduce brain inflammation and improve certain neurotransmitter activity – all of which can affect memory, alertness and mood.

Tea’s benefits may extend further because of its lower caffeine content, potentially allowing higher consumption without the negative effects that can occur with excessive coffee intake.

Implications for public health and industry

With dementia rates expected to rise in ageing populations, the findings highlight low-cost, accessible habits that may help maintain cognitive health. For the coffee and tea industries, the research adds to the functional positioning of these products.

Lead author Stephanie Rainey-Smith, from Murdoch University’s Centre for Healthy Ageing, emphasised the need for further research: "‘Moderate’ coffee and ‘moderate’ and ‘high’ tea intake may be a protective factor against cognitive decline. Randomised controlled trials are required to establish causal relationships leading to evidence-based recommendations regarding benefits of coffee and tea intake."

While the study does not give a green light to unlimited consumption, it reinforces the idea that a daily brew – enjoyed in moderation – could be a small but meaningful part of healthy ageing.

Limitations

The authors cautioned that the research has limitations. Coffee and tea intake was self-reported, which raises the possibility of recall bias, and the study did not record preparation methods such as whether participants drank black or green tea, how long it was brewed, or whether milk and sugar were added.

The cognitive tests used were short and non-standard, potentially limiting the scope of the findings. Most importantly, the results are observational and show associations rather than proof of cause and effect.