July 09, 2020
Dementia is a condition that describes various symptoms of cognitive decline. Older adults who develop dementia struggle with memory, communication, and decision-making skills. Alzheimer’s Disease is categorized as a type of dementia.
Over the past few decades, scientists have been exploring the relationships between caffeine, coffee, tea, and cognitive decline. In this article, we highlight the findings of some prominent studies on this topic.
To explore the relationship between caffeine and dementia, researchers measured the consumption of the most common caffeine sources: coffee and tea. Their study sample included 1409 participants, aged 65 to 79, from the Cardiovascular Risk Factors, Aging, and Dementia (CAIDE) study.
All participants were surveyed about health behaviors, health status, and medical history. They were particularly assessed for cognitive status, risk factors for dementia, and caffeine consumption. After an average follow-up of 21 years, a total of 61 dementia cases were identified.
The majority of participants drank 3-5 cups of coffee per day. This group had the lowest risk of dementia after considering other lifestyle and laboratory factors. There was no dose-response found, meaning that drinking more coffee did not equal a lesser odds of dementia.
Tea consumption had no association with dementia. However, these results are not as strong, because the majority of participants did not drink tea.
This study adjusted for a variety of know dementia risk factors: age, place of residence, diabetes, heart attack or stroke incidence, body mass, smoking, and more. They even considered a gene that is thought to be associated with dementia. The results of this study remained significant after these adjustments, meaning the relationship between coffee and dementia were not explained away by a different risk factor.
Other studies of caffeine and dementia have found mixed results. In a review, researchers identified nine studies with varying sample sizes and follow up periods. Including the CAIDE study above, four studies found significant associations between caffeinated drinks and cognitive decline.
Source: Caffeine as a Protective Factor in Dementia and Alzheimer's Disease
There was a range of findings involving both coffee and tea as sources of caffeine. Two studies found protective effects of coffee, and two studies found protective effects of tea. However, each study measured consumption differently. Does daily consumption refer to one cup a day or 3-5 cups a day? Did the study survey dementia incidence for 1 year or 10 years? These factors, along with many others, must be considered when assessing these mixed results.
What we do know is that caffeine in coffee or tea may be associated with a reduced risk of dementia, but we do not know why. Is caffeine itself stimulating the nervous system in a preventative way? Does caffeine make individuals more likely to practice dementia-preventing behaviors like reading and talking to close friends? Could other ingredients of coffee or tea be responsible for the association instead? These are the kinds of questions that further research will aim to answer.
