According to the US Food and Drug Administration, nearly 90 percent of people worldwide consume about 200 milligrams of caffeine each day. That’s equivalent to about one strong cup of coffee a day. Writing in “Nature Neuroscience”, Johns Hopkins University researchers say their findings show caffeine boosts certain memories for up to 24 hours after being ingested.
“We’ve always known that caffeine has cognitive-enhancing effects, but its particular effects on strengthening memories and making them resistant to forgetting has never been examined in detail in humans,” said senior author of the paper Michael Yassa, formerly of Johns Hopkins and now the University of California, Irvine. “We report for the first time a specific effect of caffeine on reducing forgetting over 24 hours.”
Conducting a double-blind trial, the researchers worked with a test group of people who didn’t regularly consume caffeinated products. Five minutes after studying a series of images, the test subjects were given either a placebo or a 200-milligram caffeine tablet.
To check the caffeine levels of their test subjects, the research team took saliva samples from them before they took their tablets and again one, three and 24 hours afterwards.
Both groups of test participants (those who took the placebo and those who took the caffeine tablet) were tested the following day to see if they recognized images they’d seen the previous day.
The test included showing the test subjects another series of images that included some new images, those that were shown the previous day, as well as other images that were similar, but not the same as those they had viewed earlier.
The researchers found that more members of the group who were given the caffeine tablets were able to correctly identify some of the new images as “similar” to previously viewed images rather than incorrectly identifying them as the same.
Being able to recognize the difference between two similar but not exactly alike items is called pattern separation, which is something, according to the researchers, that reveals a greater level of memory retention.
Only a few studies on the effect of caffeine on long-term memory have been conducted previously, and those that had been done did not provide much detail, according to the researchers. Those studies suggested caffeine had little or no effect on long-term memory retention.
The research team said its research was different from prior studies because its test subjects took their caffeine tablets after looking at and trying to memorize the images they were shown.
“The next step for us is to figure out the brain mechanisms underlying this enhancement,” said Yassa. “We can use brain-imaging techniques to address these questions. We also know that caffeine is associated with healthy longevity and may have some protective effects from cognitive decline like Alzheimer’s disease. These are certainly important questions for the future.”