Polyphenol Intake and Risk of Dementia and Cognitive Decline in Older Adults: Principal Component Analysis Approach

Polyphenols have been associated with brain health, but their impact on humans, especially in combinations, has been less explored.

This study aimed to investigate the association between dietary polyphenol patterns (PPs), dementia incidence, and cognitive changes over time in the elderly.

A total of 1041 individuals without dementia (mean age 73.1, standard deviation [SD] = 4.9) were followed longitudinally. Participants provided baseline dietary data via a validated food frequency questionnaire. Dementia was diagnosed through clinical and neuropsychological evaluations, and cognitive performance was assessed using a neuropsychological battery. Principal component analysis of 11 polyphenol classes identified 3 distinct PPs. Generalized Estimating Equations assessed cognitive decline rates, whereas Cox regression models evaluated dementia risk, adjusting for covariates such as age, sex, education, energy intake, physical activity, smoking, alcohol consumption, hypertension, diabetes mellitus, stroke history, coronary disease, and baseline mild cognitive impairment.

Over the follow-up period of 3.0 y (SD = 0.8), 62 participants developed dementia. The PPs explained up to 77.4% of the variance. The third polyphenol pattern (PP3), characterized by lignans, flavonols, and isoflavonoids, predominantly provided by cruciferous vegetables, pulses, and leafy vegetables, was associated with a slower rate of cognitive decline. A 1-unit increase in PP3 intake was associated with 0.9% of a SD less decline per year in the global cognitive score (β = 0.009; 95% confidence interval [CI]: 0.000, 0.017, P = 0.041). For incident dementia, participants in the third quartile of PP3 had a 71% lower risk than those in the first quartile (hazard ratio [HR]: 0.29; 95% CI: 0.12, 0.67, P-trend = 0.018). No significant associations were observed for the other PPs.

A PP high in lignans, flavonols, and isoflavonoids was associated with a reduced risk of dementia and cognitive decline in elderly Greeks. These findings offered encouraging evidence for combined polyphenol intake, suggesting further validation in different population samples.