The cohort included 521,448 men and women (aged 25-70 years) from the general population who entered the study in 1991 through 2000. In addition to those in the general population, some participants were members of a health insurance scheme for state school employees (France), were attending breast cancer screening (Utrecht, the Netherlands and Naples, Italy), were blood donors (centers in Italy and Spain), and were predominantly vegetarians (Oxford "health conscious" cohort). Participants completed a diet and lifestyle questionnaire, which included extent of tea and coffee consumption. Blood was collected and anthropometric (body) measurements were collected. Cancer diagnoses were obtained from population-based cancer registries.

The final data set included 410,309 participants with a mean follow-up of 8.5 years. Participants were excluded if they had missing dietary data, missing histology (all of France), incomplete follow-up, or cancer at baseline. A total of 343 glioma (165 men, 178 women) and 245 meningioma (54 men, 191 women) cases were reported. The authors decided to combine coffee and tea intake based on the hypothesis that caffeine may play a role in the risk for glioma. Mean coffee and tea consumption varied regionally across Europe. For example, England consumed the most tea, and Denmark consumed the most coffee. Higher volumes of coffee and tea tended to be consumed by participants who were slightly older, more educated, current smokers, and had a lower body mass index (BMI).    

Taking into account the regional differences in coffee/tea consumption, the analyses showed no relationship between coffee or tea intake and either glioma or meningioma risk. The findings were similar for men and women. When considering the volume of intake, there was no association between coffee/tea intake and glioma or meningioma risk. However, when data were analyzed based on a consumption cut-off of 100 mL/day, associations were found. Daily coffee/tea consumption of ≥ 100 mL was associated with a lower risk of glioma (P = 0.03). This association was consistent across 6 of the 7 countries assessed; however, the data were not statistically significant for the individual countries. The association was stronger for men than for women. Soft drinks, menopausal status, or oral contraceptive use did not alter the findings. There was no association between meningioma risk and the 100 mL/day cut-off.

The authors hypothesize that since there was no association between consumption and meningioma risk, then coffee/tea may be acting late in the process of carcinogenesis by preventing tumor growth. Since brewing methods differ, the quantity of caffeine in coffee/tea may vary. Therefore, the total volume of coffee/tea consumed may not reflect the amount of caffeine consumed. For example, 1 oz of espresso has almost as much caffeine as 8 oz of drip coffee. Europeans do not drink much decaffeinated coffee/tea so this could not be factored into the calculations. Both this European study and the US study showed a lower risk of glioma with a higher intake of coffee/tea, indicating that the findings are not due to chance alone. The constituent(s) responsible for the action is(are) unknown.