Green tea consumption and dementia risk in community-dwelling Japanese people aged 40-74 years: A 12-year cohort study

Abstract

Objective: Green tea, like coffee, has been suggested to protect against dementia, but supporting evidence is lacking. The present study aimed to determine independent associations of green tea consumption with, and interactions of green tea and coffee consumption on, dementia risk in middle-aged and older people.

Methods: The present study is a 12-year follow-up of the Murakami cohort study on age-related diseases. Participants were 13,660 (men, 6,573 [48.1%]; mean age, 59.0 (SD = 9.3) years) community-dwelling residents aged 40-74 years. The baseline survey was conducted between 2011-2013. A self-administered questionnaire obtained information on predictors, including sex, age, marital status, education, occupation, body size, physical activity, smoking, alcohol, tea and coffee consumption, energy intake, and medical history. Green tea consumption was quantitatively determined with a validated questionnaire. Cases of incident dementia were identified using the long-term care insurance database.

Results: Higher green tea consumption was associated with lower hazard ratios (HRs) for dementia (multivariable P for trend = 0.0178), with the highest quartile having a lower HR (adjusted HR = 0.75) than the lowest quartile. The adjusted HR for dementia by cup-based green tea consumption (1 cup = 150 mL) was 0.952 (95%CI:0.92-0.99), corresponding to a 4.8% reduction per 1 cup increase. High consumption of both green tea and coffee was not associated with low dementia risk (P for interaction = 0.0210).

Conclusion: Higher consumption of green tea is independently associated with a lower risk of dementia. Although green tea was found to be beneficial, excessive consumption of both green tea and coffee is not recommended for the prevention of dementia.

Keywords: Alzheimer’s disease; Coffee; Cohort study; Dementia; Green tea; Interaction.

Fig. 1

Adjusted hazard ratios (HRs) for dementia according to combined quartile-based green tea and coffee consumption, with the Q1 (<94-mL-green tea and <25-mL-coffee) group as the reference. Asterisks (*) denote HRs that are significantly lower or higher than the reference. Overall, HRs tended to decrease with increasing consumption of green tea and coffee, except for the Q4 (≥600 mL-green tea and ≥300 mL-coffee) groups. P for interaction of green tea and coffee consumption (both continuous variables) on dementia hazards was 0.0210.