So far, studies on coffee's long-term effect on cognitive function have had conflicting results, with both benefits and adverse effects reported.
A meta-analysis led by the University of South Australia explored the causal association between habitual coffee consumption and cognitive function in mid- to later life in 415,530 participants of European descent from 10 cohorts in total, among which 300,760 were regular coffee drinkers.
Caffeine and cognition
Each cohort had participants' global cognition and memory assessed using composite scores, with a genetic score to gauge the effects of habitual coffee intake.
The researchers reported that they did not observe expected (positive or negative) results across most of the studies when looking at the link between genetic scores and global and memory cognition.
Domain-specific analyses based on cognitive measures "also did not support effects by habitual coffee intake for reaction time, pairs matching, reasoning or prospective memory".
They added that their large-scale genetic analyses of the coffee drinkers produced no evidence on either the positive or negative effects of coffee consumption on global cognition or memory.
The null findings reported were consistent across cohorts, but the researchers wrote: "While our analyses did not provide evidence for long-term benefits, these data suggest that there are no adverse effects on memory or cognitive function."
Secondary analyses of the relationship between genetic scores and habitual intake of both coffee and tea were also conducted.
From these, the researchers observed that those who consumed more coffee tended to drink less tea, but the genetic factors related to the consumption of both coffee and tea were similar.
This led them to state that changes in caffeine metabolism were responsible for the link between genetic scores and habitual coffee intake.
Safe but ineffective?
While coffee consumption has been associated with a number of health benefits, including protection against arrhythmia, sarcopenia prevention, and improvements in sleep quality and energy metabolism, but its effects on memory and overall cognitive function remain less clear, especially in the long term.
The researchers wrote in conclusion: "We found no evidence that habitual coffee consumption is causally associated with global and memory cognition in mid- to later life, despite the power to detect very small effects.
"This suggests that interventions to protect cognition or slow cognitive decline using coffee are unlikely to be successful and should not be prioritised in future trials.
"That said, there was no evidence for any adverse effect, contrary to some previous observational studies, and hence, it appears safe to consume coffee at least with respect to preserving memory function."
Source: Scientific Reports
https://doi.org/10.1038/s41598-018-25919-2
"Habitual coffee consumption and cognitive function: a Mendelian randomization meta-analysis in up to 415,530 participants"
Authors: Ang Zhou, et al.