By Ellen Feldman, MD
Altru Health System, Grand Forks, ND
SUMMARY POINTS
- This U.K. study following 365,682 individuals investigated an association between self-reported coffee and tea consumption at baseline and development of stroke, dementia, and/or poststroke dementia over a median of 11.4 years.
- When compared with nondrinkers of coffee and/or tea, a daily habit of drinking 2-3 cups of coffee and 2-3 cups of tea reported at baseline was associated with a 32% lower risk of stroke (P < 0.001), while 0.5-1 cup coffee combined with > 4 cups tea daily was associated with a 30% lower risk of dementia (P < 0.001).
- Daily drinking of 0.5-1 cup of coffee in conjunction with 2-3 cups tea reported at baseline was associated with the lowest risk of poststroke dementia (hazard ratio of 0.52; P = 0.007).
SYNOPSIS: A long-term, large-scale prospective U.K. study finds moderate amounts of coffee and/or tea consumption is associated with the lowest hazard ratio of stroke and dementia, while coffee alone or in combination with tea is 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 that 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 that there have been studies linking coffee or tea to a lowered risk of stroke or dementia. However, the results of these studies have been inconsistent, inconclusive, and have not investigated the potential of a multiplicative effect on health benefits among individuals who regularly consume both beverages. The aim of this work was to assess the association of each beverage (coffee and tea) individually and in combination to 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) was analyzed for this study.4 Elimination of patients younger than 50 years of age 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, 2-3 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 preparation.)
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 decreased risk of stroke. Specifically, when 2-3 cups of either beverage were consumed daily, the risk of stroke decreased 12% to 16% (hazard ratio [HR], 0.84-0.88) when compared with participants who were not coffee or tea drinkers. This relationship does not appear linear in nature. (See Tables 1 and 2.)
Table 1. Risk of Stroke for Coffee Drinkers vs. Noncoffee Drinkers
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|
Amount of Beverage Consumed
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Hazard Ratio (95% CI)
|
P Value
|
|
0.5-1 cup of coffee daily
|
0.90 (95% CI, 0.85-0.95)*
|
P < 0.001*
|
|
2-3 cups of coffee daily
|
0.88 (95% CI, 0.84-0.94)*
|
P < 0.001*
|
|
> 4 cups of coffee daily
|
0.92 (95% CI, 0.86-0.98)
|
P = 0.009
|
|
*Statistically significant values
CI: confidence interval
|
Table 2. Risk of Stroke for Tea Drinkers vs. Nontea/Noncoffee Drinkers
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|
Amount of Beverage Consumed
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Hazard Ratio (95% CI)
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P Value
|
|
0.5-1 cup of tea daily
|
0.97 (95% CI, 0.89-1.04)
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P = 0.386
|
|
2-3 cups of tea daily
|
0.84 (95% CI, 0.79-0.80)*
|
P < 0.001*
|
|
> 4 cups of tea daily
|
0.84 (95% CI, 0.79-0.90)*
|
P < 0.001*
|
|
*Statistically significant values
CI: confidence interval
|
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 further reduced 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 2-3 cups of each beverage daily. This combination resulted in a 32% lower risk for stroke and 38% lower risk for ischemic stroke compared to nondrinkers of either beverage. (See Table 3.) There was no statistical significance for an association with hemorrhagic stroke.
Table 3. Hazard Ratio for Stroke Risk for 2-3 Cups of Coffee and Tea Daily Compared to Drinking Neither
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2-3 Cups of Coffee and Tea Daily and Risk of Stroke
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2-3 Cups of Coffee and Tea Daily and Risk of Ischemic Stroke
|
|
Hazard ratio (95% CI)
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0.68 (95% CI, 0.59-0.79)*
|
0.62 (95% CI, 0.51-0.75)*
|
|
P value
|
P < 0.001*
|
P < 0.001*
|
|
*Statistically significant values
CI: confidence interval
|
DEMENTIA RISK
Results indicate that 2-3 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. (See Tables 4 and 5.)
Table 4. Risk of Dementia for Coffee Drinkers vs. Noncoffee/Nontea Drinkers
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|
Amount of Beverage Consumed
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Hazard Ratio (95% CI)
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P Value
|
|
0.5-1 cup of coffee daily
|
0.94 (95% CI, 0.87-1.02)
|
P = 0.147
|
|
2-3 cups of coffee daily
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0.93 (95% CI, 0.85-0.98)*
|
P < 0.014*
|
|
> 4 cups of coffee daily
|
0.96 (95% CI, 0.88-1.06)
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P < 0.424*
|
|
*Statistically significant values
CI: confidence interval
|
Table 5. Risk of Dementia for Tea Drinkers vs. Nontea/Noncoffee Drinkers
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|
Amount of Beverage Consumed
|
Hazard Ratio (95% CI)
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P Value
|
|
0.5-1 cup of tea daily
|
0.92 (95% CI, 0.82-1.03)
|
P = 0.135
|
|
2-3 cups of tea daily
|
0.92 (95% CI, 0.84-1.01)
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P < 0.064
|
|
> 4 cups of tea daily
|
0.89 (95% CI, 0.82-0.98)*
|
P < 0.014*
|
|
*Statistically significant values
CI: confidence interval
|
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 further reduced for respondents who recorded drinking both coffee and tea daily when compared with 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 > 4 cups of tea daily. (See Table 6.) 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.
Table 6. Hazard Ratio for Dementia Risk for 0.5-1 Cup of Coffee and > 4 Cups of Tea Daily Compared to Drinking Neither
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0.5-1 Cup of Coffee and > 4 Cups Tea Daily and Risk of Dementia
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0.5-1 Cup of Coffee and > 4 Cups of Tea Daily and the Risk of Vascular Dementia
|
|
Hazard ratio (95% CI)
|
0.70 (95% CI, 0.58-0.86)*
|
0.53 (95% CI, 0.37-0.76)*
|
|
P value
|
P < 0.001*
|
P < 0.001*
|
|
*Statistically significant values
CI: confidence interval
|
POSTSTROKE DEMENTIA RISK
Out of the 365,862 respondents in this study, 13,352 had a stroke and thus 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 2-3 cups daily coffee drinkers were 0.80 (95% confidence interval [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 found a lowered HR of drinking 0.5-1 cup of coffee and 2-3 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 were lowered, as shown in Table 7. Among 160,741 coffee drinkers, after multivariable analysis, ground coffee appeared to outperform both instant and decaffeinated coffee in most categories.
Table 7. Hazard Ratio for Drinking Both Coffee and Tea Compared to Participants Who Drank Only One
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|
Stroke
|
Ischemic Stroke
|
Dementia
|
Vascular Dementia
|
|
Hazard ratio (95% CI)
|
0.89 (95% CI, 0.86-0.93)*
|
0.89 (95% CI, 0.84-0.94)*
|
0.92 (95% CI, 0.87-0.98)*
|
0.82 (95% CI, 0.87-0.98)*
|
|
P value
|
P < 0.001*
|
P < 0.001*
|
P < 0.001*
|
P < 0.001*
|
|
*Statistically significant values
CI: confidence interval
|
COMMENTARY
This prospective study shows that coffee or tea intake is associated with a lowered risk of stroke, ischemic stroke, dementia, and vascular dementia, and that the combined use of these beverages is 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 lowered risk of development of dementia poststroke. Zhang et al postulated that 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 have 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 of this study, adding to the ability to generalize findings with confidence. One major limitation of the study is that 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, 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 that 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 that associations found in the study do not imply causation, that the association of these beverages with reduction of risk was nonlinear (more is not necessarily better in this regard), and that 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 that moderate intake of coffee and or tea or approximately 2-3 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. https://www.pewresearch.org/fact-tank/2013/12/20/chart-of-the-week-coffee-and-tea-around-the-world/
- 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. Updated Jan. 20, 2022. https://www.ukbiobank.ac.uk
