Objective:

To investigate the association between caffeinated coffee and tea consumption and the risk of dementia, particularly Alzheimer's disease.

Key Findings:

• Higher caffeinated coffee consumption (2-3 cups daily) was associated with a 0.82 times lower likelihood of developing dementia (p<0.05).
• Incidence rate of dementia was 141 per 100,000 person-years in the highest coffee consumption group versus 330 in the lowest (p<0.01).
• Higher tea intake also correlated with lower dementia risk, with a 0.86 times lower likelihood in the highest tertile (p<0.05).
• Decaffeinated coffee showed no significant association with dementia risk (p>0.05).
• Subjective cognitive decline prevalence was lower in the highest coffee intake group (8%) compared to the lowest (10%).

Interpretation:

Moderate consumption of caffeinated coffee and tea is linked to a reduced risk of dementia and improved cognitive function, particularly in younger participants (aged 75 years or younger).

Limitations:

• Reliance on food frequency questionnaires that did not specify tea types or coffee preparation methods.
• Dementia ascertainment based on death records and self-reported diagnoses may lead to misclassification.
• Potential reverse causation despite sensitivity analyses.
• Objective cognitive outcomes were only measured in the NHS cohort without independent replication.
• Lack of diversity in the study population may limit generalizability.

Conclusion:

Greater consumption of caffeinated coffee and tea is associated with lower dementia risk and modestly better cognitive function, with optimal benefits observed at moderate intake levels (2-3 cups daily).