Coffee and Tea: Drink Choice and Effects on Stroke, Dementia, and Poststroke Dementia
By Ellen Feldman, MD
Altru Health System, Grand Forks, ND
SYNOPSIS: Moderate amounts of coffee and/or tea consumption were associated with the lowest hazard ratio of stroke and dementia, while coffee alone or in combination with tea was associated with a lower risk of poststroke dementia.
SOURCE: Zhang Y, Yang H, Li S, et al. Consumption of coffee and tea and risk of developing stroke, dementia, and poststroke dementia: A cohort study in the UK Biobank. PLoS Med 2021;18:e1003830.
Ask for tea or coffee anywhere in the world, and chances are good one or both will be available. These drinks are among the most popular beverages across the globe, with general preferences varying region to region.
For example, while coffee is more dominant in the United States and parts of Europe, tea is the more typical beverage of choice in most of Asia and eastern Europe.1 Both drinks contain caffeine and a host of other biologically active compounds, such as antioxidants in coffee and neuroprotective catechin polyphenols and flavonoids in tea, suggesting the likelihood of an effect on health and specific disease states. Given the overall prevalence of these drinks, potential health benefits and risks can have significant public health implications.1-3
Zhang et al noted there are studies linking coffee or tea to a lowered risk of stroke or dementia. However, the results of these studies have been inconsistent and inconclusive. Those authors did not investigate the potential of a multiplicative effect on health benefits among individuals who regularly consume both beverages. The aim of the Zhang et al study was to assess the association of each beverage (coffee and tea) individually and in combination with the development of dementia, stroke, and poststroke dementia.
Data from individuals enrolled in the U.K. Biobank (a population-based cohort with information collected from 2006-2010) were analyzed for this study.4 Elimination of patients younger than age 50 years at baseline and individuals with a history of stroke or dementia at baseline yielded a group of 365,682 eligible records for this analysis.
Respondents were asked to record an average daily quantity of coffee and tea intake at baseline. Categories of daily consumption were created, starting with 0 to 0.5-1 cups, two to three cups, or > 4 cups. The type of tea was not specified, but respondents were asked to note if coffee was caffeinated, ground, or brewed. These categories for coffee often overlapped. Many individuals drank both decaffeinated and caffeinated and both ground and brewed preparations.
Outcome measures were stroke and dementia. Diagnoses were collected until 2020 from ICD-10 codes, allowing subdivision into ischemic and hemorrhagic stroke and Alzheimer’s dementia and vascular dementia, respectively. The median follow-up was 11.4 years. Covariates included age, ethnicity, socioeconomic status, smoking status, alcohol use, level of physical activity, and healthy/unhealthy dietary pattern. An additional outcome measure was poststroke dementia, which refers to any type of dementia with onset after a stroke.
STROKE RISK
In this study, any quantity of tea or coffee measured (in cups/day) appeared to be associated with a lower risk of stroke. Specifically, when two to three cups of either beverage was consumed daily, the risk of stroke decreased 12% to 16% (HR, 0.84-0.88) vs. participants who were not coffee or tea drinkers. This relationship does not appear linear in nature.
When comparing subtypes of stroke, coffee and tea each were associated with a lower risk of ischemic stroke in all categories, but there was no association with a lowered risk of hemorrhagic stroke. Risk was even lower for respondents who recorded drinking both coffee and tea daily. There were multiple permutations of this combination, but the most statistically significant reduction in risk was associated with those who reported consuming two to three cups of each beverage daily. This combination resulted in a 32% lower risk for stroke and 38% lower risk for ischemic stroke vs. nondrinkers of either beverage. There was no statistical significance for an association with hemorrhagic stroke.
DEMENTIA RISK
Results indicate drinking two to three cups of coffee daily or > 4 cups of tea daily were associated with a reduced risk of dementia of 7% and 11%, respectively, when compared with either noncoffee or nontea drinkers. When comparing subtypes of dementia after multivariable adjustment, both coffee and tea consumption were associated with a lower risk of dementia and vascular dementia, but not Alzheimer’s dementia.
As with stroke risk, dementia risk was even lower for respondents who recorded drinking both coffee and tea daily vs. nondrinkers of either beverage. Again, there were multiple combinations regarding quantity of tea and coffee daily, with the largest risk reduction seen at 0.5-1 cup of coffee and more than four cups of tea daily. Notably, the risk reduction was larger when an association with vascular dementia was isolated. There was no significant association with this combination of beverages and the onset of Alzheimer’s dementia.
POSTSTROKE DEMENTIA RISK
Out of the 365,862 respondents in this study, 13,352 had a stroke and were followed for incidence of poststroke dementia. Over a median follow-up period of 7.07 years, 646 developed dementia (119 with Alzheimer’s disease and 315 with vascular dementia). Compared to noncoffee drinkers and after multivariable adjustment, HRs for any poststroke dementia for two to three cups daily coffee drinkers were 0.80 (95% CI, 0.64-0.99; P = 0.044). No significant statistical association was found with either Alzheimer’s or vascular dementia.
Compared to nontea drinkers and after multivariable adjustment, HRs for any poststroke dementia for tea drinkers were not statistically significant. Compared to participants drinking neither coffee nor tea, a multivariable adjustment model revealed a lowered HR of drinking 0.5-1 cup of coffee and two to three cups of tea daily of 0.50 (95% CI, 0.31-0.82; P = 0.0006 for any poststroke dementia, but no association with either Alzheimer’s or vascular dementia).
OTHER FINDINGS
When compared with respondents who drank only coffee or only tea, the multivariable adjusted HR for those who drank both beverages was lowered. Among 160,741 coffee drinkers, after multivariable analysis, ground coffee appeared to outperform both instant and decaffeinated coffee in most categories.
COMMENTARY
This prospective study shows coffee or tea intake is associated with a lower risk of stroke, ischemic stroke, dementia, and vascular dementia. The combined use of these beverages was associated with an even lower risk of these outcomes. In addition, consumption of coffee alone or of coffee and tea combined was associated with a lower risk of development of dementia poststroke. Zhang et al postulated heightened protection from stroke and dementia in individuals drinking both coffee and tea may stem from potentiation between bioactive compounds in each beverage. For example, both coffee and tea include polyphenolic content (potentially helpful in endothelial function and anti-inflammation) with different target molecules.2,3 Further study in this area may open more information about such mechanisms and pathways.
The large number of participants in this study and long-term follow-up are clear strengths, adding to the ability to generalize findings with confidence. One major limitation was the fact documentation of beverage use was only completed at baseline. Without additional information regarding beverage consumption over the follow-up period, it is difficult to know how to translate this study into clinical guidelines. Hopefully, the authors of future studies will collect data over time and find a method of data collection that is more objective than self-report. New methodology also could assist in determining any association with health outcomes when looking at specific types and preparations of coffee and/or tea. Additional concerns limiting generalization are the fact the U.K. Biobank cohort tends to be a relatively healthy group at baseline. Expanding such studies to more diverse populations will assist in applying findings in the future.
For now, these results may be applied clinically with caution, noting associations revealed here do not imply causation, the association of these beverages with reduction of risk was nonlinear (more is not necessarily better in this regard), and additives, such as cream and sugar, could change the health benefits of these beverages. At a minimum, this study may serve as a reminder of the importance of diet in an overall health and wellness plan. In addition, this investigation can give a provider the confidence to let patients know moderate intake of coffee and or tea (approximately two to three cups of each beverage), and (potentially) a combination of these beverages, may convey valuable health benefits.
REFERENCES
- DeSilver D. Chart of the Week: Coffee and tea around the world. Pew Research Center. Published Dec. 20, 2013.
- Poole R, Kennedy OJ, Roderick P, et al. Coffee consumption and health: Umbrella review of meta-analyses of multiple health outcomes. BMJ 2017;359.j5024.
- Khan N, Mukhtar H. Tea and health: Studies in humans. Curr Pharm Des 2013;19:6141-6147.
- U.K. Biobank.
Moderate amounts of coffee and/or tea consumption were associated with the lowest hazard ratio of stroke and dementia, while coffee alone or in combination with tea was associated with a lower risk of poststroke dementia.
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