Can drinking coffee and tea lower the risk of dementia or stroke?

A group of researchers from China’s Tianjin Medical University found that drinking the caffeinated beverages either separately or together was associated with a lower risk of developing stroke and dementia.

Additionally, the authors said Tuesday in a study published in Plos Medicine that the intake of coffee alone or combined with tea was associated with a lower risk of post-stroke dementia.

In order to reach these conclusions, the study included 365,682 participants from the UK Biobank who were 50 to 74 years old.

The participants, who joined the study from 2006 to 2010, reported their coffee and tea consumption. They were followed up until last year.

In order to estimate the associations between consumption and incidents of stroke and dementia, the group used Cox proportional hazards models, adjusting for several factors like sex, age, ethnicity, income, body mass index (BMI), alcohol and smoking status, diet pattern, and physical activity.

During an average follow-up of 11.4 years for new-onset disease, 5,079 participants developed dementia and 10,053 participants developed stroke.

Drinking two to three cups of coffee a day, three to five cups of tea in the same period, or the combined intake of four to six cups per day were linked with the lowest hazard ratio of stroke and dementia.

The authors also found that drinking two to three cups of coffee with two to three cups of tea daily was associated with a 32% lower risk of stroke and a 28% lower risk of dementia.

They said the findings highlighted the potentially beneficial relationship between coffee and tea consumption and risk of stroke, dementia and post-stroke dementia, “although causality cannot be inferred.”

Limitations to the study included that intake was self-reported at baseline and may not reflect long-term consumption patterns, that “unmeasured confounders” may result in biased effect estimates in observational studies, and that UK Biobank participants are not representative of the whole U.K. population.

Roughly 80% of U.S. adults consume caffeine every day, according to the U.S. Centers for Disease Control and Prevention (CDC).