Women who consumed the equivalent of two to three cups of coffee daily were found to be at lower risk of dementia and cognitive impairment.
Researchers have long suggested that caffeine - a mild stimulant present in coffee, tea, and cola - has cognitive benefits.
A study published in the journal Nature Neuroscience in 2014, for example, identified a link between coffee intake and improved long-term memory.
The new findings - recently published in The Journals of Gerontology, Series A: Biological Sciences and Medical Sciences - offer further evidence of caffeine's brain benefits, after finding the stimulant may help to stave off cognitive decline in later life.
The results come from an analysis of 6,467 women aged 65 and older who were part of the Women's Health Initiative Memory Study (WHIMS) - a study funded by the National Heart, Lung, and Blood Institute.
"What is unique about this study is that we had an unprecedented opportunity to examine the relationships between caffeine intake and dementia incidence in a large and well-defined, prospectively studied cohort of women," notes lead author Ira Driscoll, Ph.D., a professor of psychiatry at the University of Wisconsin-Milwaukee.
Higher caffeine intake reduced risk of cognitive impairment, dementia
Driscoll and team analyzed the participants' caffeine intake, as determined through self-reported consumption of tea, coffee, and cola.
- Around 54 percent of American adults drink coffee every day
- Coffee drinkers consume an average of 3.1 cups daily
- The U.S. spends around $40 billion on coffee every year.
During up to 10 years of follow-up, all subjects underwent annual cognitive assessments, which the researchers analyzed to pinpoint a diagnosis of probable dementia or other forms of cognitive impairment. A total of 388 women received such diagnoses.
Compared with women who consumed a low amount of caffeine (defined in the study as less than 64 milligrams daily), those who consumed a higher amount (more than 261 milligrams daily) were found to be at 36 percent reduced risk of a diagnosis of probable dementia or cognitive impairment.
The researchers note that 261 milligrams of caffeine is the equivalent of two to three 8-ounce cups of coffee daily, or five to six 8-ounce cups of black tea.
The team's findings remained even after accounting for a number of possible confounding factors, including age, race, body mass index (BMI), smoking status, alcohol intake, depression, high blood pressure, sleep quality, and history of cardiovascular disease.
The authors say that their study is unable to establish a direct association between caffeine intake and reduced dementia risk, nor are they able to generalize the findings to men.
Still, the researchers believe that their study brings us closer to understanding how caffeine might benefit cognitive health, and it paves the way for future research into this association.
The authors conclude:
"Although more studies are needed to verify the consistency of reports, given that caffeine intake is easily modifiable, it is important to quantify its relationship with cognitive health outcomes not only from preventive standpoint but also to better understand the underlying mechanisms and their involvement in dementia and cognitive impairment.
Given that AD [Alzheimer's disease] prevalence is expected to quadruple by 2050, even a small reduction in age-related cognitive impairment or dementia burden would thereby have significant public health implications."
Why might coffee have cognitive benefits?
Medical News Today asked Driscoll what she believes are the underlying mechanisms that might explain caffeine's potential cognitive benefits.
"The potential protective effect of caffeine is thought to occur primarily through the blockade of adenosine A2A receptors (ARs), whose expression and function become aberrant with both normal aging and age-related pathology," she replied.
"Adenosine acts by facilitating A2A and acting on the inhibitory A1 receptors to integrate dopamine, glutamate, and brain-derived neurotrophic factor signaling, thereby modulating synaptic plasticity in regions relevant to learning and memory and providing the molecular and cellular basis for AR role in modulating cognition," she added.
Additionally, Driscoll said that ARs are being increasingly investigated as a target for reversing cognitive impairment; studies have shown that blocking these receptors can reverse Alzheimer's and other neurodegenerative disorders in animal models.
While the findings may be welcome news for coffee drinkers, Driscoll told MNT that women should not increase their coffee intake based on the results.
"It remains unknown if this holds primarily for caffeine derived from coffee or other dietary sources," she said, "and we are certainly not suggesting that more is better."