Could drinking a certain amount of coffee or tea help lower dementia risk?

People with high blood pressure can be at an increased risk for dementia. Researchers of the current study note that abnormal blood pressure is linked to about 11-20% of dementia cases.

Verna Porter, MD, a board certified neurologist and director of the Dementia, Alzheimer’s Disease and Neurocognitive Disorders at Pacific Neuroscience Institute in Santa Monica, CA, who was not involved in the study, explained how hypertension contributes to increased dementia risk to Medical News Today:

“Hypertension, particularly in midlife, is a well-established risk factor for dementia, including both vascular dementia and Alzheimer’s disease. High blood pressure can cause damage to the blood vessels in the brain, leading to reduced cerebral perfusion and microvascular damage. This, in turn, contributes to cognitive decline.”

“Over time, chronic hypertension may lead to the accumulation of small infarcts, white matter lesions, and disruption of the blood-brain barrier, all of which increase the risk of neurodegenerative processes. Moreover, hypertension is closely linked with other vascular risk factors, such as diabetes and hyperlipidemia, further increasing the risk of cognitive impairment,” she continued.

This research examined the relationship between drinking coffee and tea and dementia risk. The researchers used data from the U.K. Biobank and analyzed 453,913 participants.

Over half of these participants had high blood pressure, and the average age of participants was around 72 years. The average follow-up time with participants was around 15 years. Researchers excluded participants who already had dementia at baseline and who had secondary high blood pressure.

Because of the data available via the U.K. Biobank, researchers had large amounts of data to work with, from the types of coffee participants consumed to information on health conditions and lifestyle.

After adjusting for covariates, the researchers found that individuals with high blood pressure still had a greater risk for all-cause dementia, Alzheimer’s disease, and vascular dementia than people who did not have high blood pressure.

In further analyses, the researchers wanted to examine the relationship between tea and coffee consumption and dementia risk. They adjusted for different factors, with models considering more aspects of participants’ lives, like lifestyle factors and health components.

Researchers identified a J-shaped relationship between coffee and all-cause dementia among participants with high blood pressure. J-shaped and U-shaped relationships indicate a lower risk for something in the middle ground of consumption rather than no consumption or high consumption levels.

They found that participants with high blood pressure who drank one-half and one cup of coffee daily had the lowest chances of developing all-cause dementia. This was in comparison to individuals with high blood pressure who consumed six or more cups of coffee daily.

The researchers next identified a U-shaped association between drinking tea and risk for all-cause dementia among participants with high blood pressure. Participants who drank four to five cups of tea daily had the lowest risk for all-cause dementia.

In contrast to these findings on tea and coffee, the researchers found no association between drinking tea or coffee and all-cause dementia, Alzheimer’s disease, or vascular dementia among participants without high blood pressure.

When examining tea and coffee together, the researchers found that participants with high blood pressure who had four to five cups of coffee and six or more cups of tea a day had the lowest chances of developing Alzheimer’s disease and all-cause dementia. This was in comparison to people who did not drink tea but still drank six or more cups of coffee in a day.

However, the researchers did note in the discussion that consuming large amounts of caffeine could be harmful and even increase dementia risk.

Does type of coffee matter?

They also found that the type of coffee consumed appeared to have an effect with ground coffee associated with the lowest risk for all-cause dementia and vascular dementia among all participants compared to drinking decaf coffee.

Finally, the researchers looked at caffeine intake and dementia risk. They found a U-shaped association between caffeine and risk for vascular and all-cause dementia among participants with high blood pressure.

They observed a W-shaped association among participants without high blood pressure, indicating that certain levels of caffeine consumption were associated with decreased risk. In contrast, the amount between these levels was associated with increased risk.

The researchers further observed that finding a significant association between amounts of coffee and tea and all-cause and vascular dementia was more likely among participants with high blood pressure than among those who did not have high blood pressure.

Cheng-Han Chen, MD, a board certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, who was also not involved in the study, commented on this link:

“This study found an association between the consumption of coffee and tea and the risk of developing dementia, especially in those individuals with hypertension. It is important to note that while a low-moderate amount of coffee intake decreased the risk of dementia, having 6 or more cups a day appeared to increase the risk, likely related to the excessive caffeine intake.”

“For both coffee and tea, the beneficial effects on reducing the risk of dementia are likely achieved by enjoying the beverages in moderation,” he stressed.

Porter further noted the following clinical implications:

“From a clinical perspective, if further studies replicate these findings, it could pave the way for specific dietary recommendations for patients at risk of dementia, particularly those with hypertension. Allowing for consumption of coffee or tea in moderation might be one small yet impactful part of a larger prevention strategy. The study underscores the importance of controlling hypertension to reduce dementia risk and suggests that lifestyle factors, including caffeine intake, could modulate this risk.”

This study does have some limitations. First, the U.K. Biobank doesn’t necessarily reflect the general population. Most U.K. Biobank participants are white U.K. citizens, so the results may not be generalizable to other groups. The U.K. Biobank also tends to include people who are more health-conscious, so there may be underestimations regarding dementia.

Second, the study cannot establish a causal relationship between dementia and caffeine. Some data from the U.K. Biobank is reported by participants, which may be incorrect. Researchers also made assumptions about the amount of caffeine in servings of coffee and tea.

The authors acknowledge that there may be information bias in the self-reported baseline intake of coffee and tea. They also acknowledge that these baseline measurements don’t necessarily reflect participant’s long-term consumption. Finally, the estimations regarding higher tea and coffee intake included data from fewer participants, which could have led to imprecisions about dementia observations.

“It remains important to consider the potential for residual confounding, especially when dealing with complex factors like diet, lifestyle, and genetic predispositions,” Porter also noted.

Porter said more research was needed before we observe changes in clinical practice:

“More data would be needed before translating these findings into broad clinical practice. [U]nderstanding the mechanisms—whether related to antioxidant properties, vascular effects, or direct actions of caffeine—would be crucial in shaping any future guidelines.”

“In practice, this study reinforces the importance of addressing vascular risk factors in dementia prevention, particularly in middle-aged patients, and points towards possible benefits from coffee and tea as part of a balanced diet. Nonetheless, it remains essential to emphasize hypertension management as a cornerstone of dementia prevention.”
— Verna Porter, MD