Alzheimer's disease is the most common type of dementia. Symptoms include serious memory loss, confusion, and mood changes that develop gradually and worsen with time.
The new study included 124 people aged 65 to 88 who had mild cognitive impairment, which is the medical term for mild memory loss. About 15% of people with MCI develop full-blown Alzheimer's disease each year.
In the study, blood levels of caffeine were more than 50% lower among people with MCI who developed Alzheimer's during follow-up, when compared with their counterparts who did not worsen. Coffee was the main, or only source, of caffeine among people in the study.
No one with mild memory loss who later developed Alzheimer's had initial blood caffeine levels above 1,200 ng/ml. This is equivalent to drinking several cups of coffee a few hours before giving blood. People whose memory loss did not progress all had blood caffeine levels higher than this level, the study shows.
"Continue to drink coffee," says researcher Chuanhai Cao, PhD. He is a neuroscientist at the University of South Florida's College of Pharmacy and Byrd Alzheimer's Institute in Tampa. "There is no reason to stop if you are experiencing memory problems."
There may even be a reason to start for people in their late 30s and up, he says. "Aim for an average of three, 8-ounce cups of coffee per day in the morning after eating breakfast."
Exactly how coffee helps delay the development of Alzheimer's is not known, but Cao has a theory. It involves beta-amyloid, a protein that accumulates in the brains of people who have Alzheimer's disease.