Association between high dietary polyphenol intake and reduced risk of dementia: A 12-year cohort study.

BACKGROUND & AIMS: Dietary polyphenols may play a modifiable role in reducing the risk of dementia; however, current evidence remains limited and inconclusive. This study aimed to investigate whether dietary polyphenol intake, taking caffeine intake into account, is associated with dementia risk in middle-aged and older people.

METHODS

Participants of this 12-year cohort study were 13,473 community-dwelling individuals aged 40-74 years (51.9% female). Dietary intake data were collected from 2011 to 2013 using a validated food frequency questionnaire. Polyphenol intake was adjusted for energy intake using the residual method. The outcome was incident dementia determined using Japan's long-term care insurance database. Multivariable Cox proportional hazards models were used to estimate adjusted hazard ratios (HRs). Covariates included demographic factors, body size, lifestyle habits, and disease history (myocardial infarction, stroke, diabetes mellitus). An additional multivariable analysis was conducted, further adjusting for energy-adjusted caffeine intake.

RESULTS

The mean age of participants was 59.1 years. During follow-up, 337 males and 331 females developed dementia. Higher polyphenol intake was associated with a lower risk of dementia (multivariable-adjusted P for trend <0.0001), with the highest quintile (Q5) having a reduced risk of dementia (HR = 0.62, 95%CI: 0.49-0.78) compared to the lowest quintile (Q1, reference). After further adjusting for energy-adjusted caffeine intake, this association remained significant (P for trend = 0.0149), with Q5 having an HR of 0.70 (95%CI: 0.52-0.95). In males, higher polyphenol intake was associated with a lower hazard of dementia (multivariable-adjusted P for trend = 0.0002), with Q4 and Q5 having a lower hazard (Q4: HR = 0.59, 95% CI: 0.42-0.83; Q5: HR = 0.55, 95%CI: 0.40-0.76) compared to Q1. In females, higher polyphenol intake was associated with a lower hazard of dementia (multivariable-adjusted P for trend = 0.0106), with Q5 having a lower hazard (HR = 0.68, 95%CI: 0.49-0.96) compared to Q1.

CONCLUSION

High polyphenol intake is robustly associated with a decreased risk of dementia in middle-aged and older individuals, with the association remaining even after accounting for caffeine intake.