High consumption of coffee or tea every day appears to protect male smokers against at least 1 type of stroke, a new study suggests.
This large, prospective, observational study showed that Finnish smokers who consumed 8 or more cups of coffee per day had a 23% lowered risk for cerebral infarction, whereas those who drank 2 or more cups of black tea daily had a 21% lowered risk for this type of stroke vs those who drank little or none of these beverages. The associations were independent of risk factors such as a history of coronary heart disease.
Their report is published in the June 2008 issue of Stroke.
Antioxidant Health Benefits
Both coffee and tea are widely consumed caffeinated beverages, the study authors write, and both are known to have antioxidant health benefits. For example, observational research suggests that coffee drinking is inversely associated with inflammation and endothelial dysfunction and that it may improve insulin sensitivity and reduce the risk for type 2 diabetes. As for tea, it contains high amounts of polyphenols, which prevent oxidation of low-density lipoprotein cholesterol and may reduce platelet activation and plasma C-reactive protein levels, a marker of inflammation.
Some of these health benefits may extend to prevention of cerebral infarction, said the study authors. "Beneficial effects of consumption of coffee and tea with regard to risk of cerebral infarction are biologically plausible because coffee and tea contain phenolic compounds with antioxidant properties that may prevent atherosclerosis," they write.
However, although the relationship between consuming caffeinated beverages and the risk for coronary heart disease has been studied extensively, this current study is among the few to examine the association with stroke risk.
Subjects for this study were participants of the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study, a randomized, double-blind, placebo-controlled primary prevention trial originally designed to determine whether alpha-tocopherol, beta-carotene, or both could reduce cancer incidence in male smokers. The cohort consisted of 29,133 Finnish men aged 50 to 69 years who smoked at least 5 cigarettes per day and had no history of stroke. From 1985 to 1988, these men were recruited into the trial, which ended in 1993.
At baseline, participants completed questionnaires gathering general background characteristics, including medical, smoking, and physical activity histories. Investigators measured height, weight, and blood pressure, calculated body mass index, and obtained levels of serum total cholesterol and high-density lipoprotein cholesterol.
Also at baseline, the researchers used validated food frequency questionnaires to assess consumption of coffee and black tea for the previous year. This information was provided by 26,556 of the randomized participants. At 2 to 5 years after randomization, the researchers asked the men how they usually prepared their coffee: filtered, boiled, or instant. This information was available for 20,427 of the participants. Most used the filter (14,513 [71.1%]) or boiling (4232 [20.7%]) method.
Calculating Caffeine Content
To calculate total caffeine consumption, researchers added the caffeine content of coffee and tea and multiplied it by the amount of consumption. For caffeine content, they used 80 mg per 100 mL of coffee and 26 mg per 100 mL of tea.
Approximately 2.5% of the study sample reported never drinking coffee, and approximately 64% did not drink tea. The mean daily coffee consumption among drinkers was 5.7 cups.
Men with higher coffee consumption were slightly younger, smoked more, had lower systolic and diastolic blood pressures, were less likely to have a history of diabetes or coronary heart disease, were more likely to be physically active, and consumed less alcohol and tea than men with low coffee consumption.
Compared with men who did not consume tea, those who did smoked slightly less, were somewhat more likely to be physically active, and consumed more alcohol but less coffee.
In their analysis, the researchers included strokes occurring from the time of randomization to December 31, 2004. During a mean follow-up of 13.6 years, there were 2702 cerebral infarctions, 383 intracerebral hemorrhages, 196 subarachnoid hemorrhages, and 84 unspecified strokes.
No Association With Other Stroke Types
After adjustment for age and cardiovascular risk factors, both coffee and tea consumption were statistically significantly inversely associated with the risk for cerebral infarction but not to other types of stroke.
Table. Multivariate Risk for Cerebral Infarction for Highest vs Lowest Category of Consumption of Coffee and TeaBeverage Relative Risk 95% CI P for Trend
Coffee 0.77 0.66 – 0.90 < .001
Tea 0.79 0.68 – 0.92 .002
The inverse relationship between coffee consumption and the risk for cerebral infarction persisted even after adjustment for history of diabetes and coronary heart disease, blood pressure, alcohol intake, and number of cigarettes smoked. As well, the associations did not differ significantly by age group, body mass index, serum total or high-density lipoprotein cholesterol levels, or physical activity.
The association was similar regardless of whether the coffee preparation method was boiling or filtered. Results also were much the same whether subjects were observed for less than 10 years or for 10 years or more.
For tea, the association between consumption and cerebral infarction also did not vary significantly by age or cardiovascular risk factors.
Because the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study includes only male smokers, the study authors write, their results may not be generalizable to women or to nonsmokers. "These findings warrant confirmation in other populations, particularly women and nonsmokers," they conclude.
The Alpha-Tocopherol Beta-Carotene Cancer Prevention Study was supported by the National Institutes of Health. First author Susanna C. Larsson's postdoctoral research at the National Public Health Institute, Helsinki, Finland, was supported by the Swedish Council for Working Life and Social Research. The other study authors have disclosed no relevant financial relationships.
Stroke. 2008;39:1681-1687.
Clinical Context
Coffee and tea consumption may ameliorate the risk for stroke through multiple physiologic effects. Coffee contains antioxidants and can improve insulin sensitivity and reduce the risk for incident type 2 diabetes. Consumption of black tea reduces platelet activation and plasma levels of C-reactive protein, a marker of inflammation linked with an increased risk for ischemic stroke.
Despite these positive physiologic effects, there is conflicting evidence as to whether coffee and tea consumption can reduce the clinical risk for incident stroke. The current study addresses this issue in a large cohort of male smokers.
Study Highlights
Study subjects were drawn from the Alpha-Tocopherol Beta-Carotene Cancer Prevention Study. Participants were Finnish men between the ages of 50 and 69 years who smoked. The study was originally designed to determine whether supplements with alpha-tocopherol or beta-carotene could prevent cancer.
Men with a history of cancer were not permitted to participate in the study, and the current study excluded subjects with a history of a previous stroke.
All subjects underwent a history and physical examination, including laboratory evaluation, at baseline. A validated food frequency questionnaire captured data regarding coffee and tea consumption.
Incident stroke and intracranial hemorrhage were identified through national registries of hospital admissions and deaths. A review of these databases confirmed that the diagnosis was accurate in the vast majority of cases.
The main outcome of the study was the effect of quintile of coffee and tea consumption on the risk for incident stroke and intracranial hemorrhage. This result was adjusted for cardiovascular risk factors and randomized study treatment.
26,556 men provided data for study analysis. The mean age was 57 years, and the mean number of cigarettes smoked daily was 20.
2.5% of subjects reported never drinking coffee, whereas 64% did not drink tea. The authors note that most Finnish men drink black tea exclusively.
The mean daily coffee intake was 5.7 cups. Quintiles of daily coffee consumption were defined as less than 2 cups, 2 to 3 cups, 4 to 5 cups, 6 to 7 cups, and 8 or more cups.
Men who drank higher levels of coffee were younger, smoked more cigarettes, and were more likely to be physically active and free of diabetes and previous coronary heart disease. There was an inverse relationship between coffee and alcohol consumption.
There were 2702 cerebral infarctions, 383 intracerebral hemorrhages, 196 subarachnoid hemorrhages, and 84 unspecified strokes during a mean of 13.6 years of follow-up.
There was a progressively decreased risk for cerebral infarction associated with higher levels of coffee consumption, with a significantly reduced risk for infarction evident at 6 to 7 cups of coffee per day. The multivariate relative risk for cerebral infarction was 0.77 in men in the highest vs lowest quintiles of coffee consumption.
Coffee consumption did not affect the risks for intracerebral hemorrhage and subarachnoid hemorrhage.
Coffee consumption was effective in reducing the risk for cerebral infarction regardless of age, blood pressure levels, lipid levels, or the presence of diabetes or heart disease.
Both filtered and boiled coffees were effective in reducing the risk for cerebral infarction.
There was also an inverse relationship between overall caffeine intake and the risk for cerebral infarction.
Tea consumption also reduced the risk for cerebral infarction, with consumption of at least 2 cups per day associated with a relative risk of 0.79 vs no tea consumption.
Similar to coffee, tea consumption did not affect rates of intracranial hemorrhage.
Pearls for Practice
Coffee contains antioxidants and can improve insulin sensitivity. Consumption of black tea reduces platelet activation and plasma levels of C-reactive protein. However, previous research has not demonstrated a consistent reduction in the risk for stroke associated with coffee or tea consumption.
The current study suggests that higher levels of coffee and tea consumption can reduce the risk for cerebral infarction among male smokers but not rates of intracranial hemorrhage.
Reviewed by Ramaz Mitaishvili, MD
