Interaction between plant-based dietary pattern and frailty on cognitive decline: a longitudinal analysis of the Chinese Longitudinal Healthy Longevity Survey cohort.

Objectives: Frailty is a risk factor for faster cognitive decline, while plant-based dietary patterns are associated with decreased risk of cognitive decline. We aimed to explore their interaction with cognitive function among older adults.

Methods: We used data from the Chinese Longitudinal Healthy Longevity Survey between 2008 and 2018. Frailty was evaluated based on the frailty index (FI), and the plant-based diet index (PDI) was calculated using food frequency questionnaire at baseline. Repeated measures of the Mini-Mental State Examination (MMSE) were utilised to assess cognitive function. We used linear mixed models to estimate regression coefficients (β) and 95% confidence intervals (CI).

Results: We included 7,166 participants with a median follow-up of 5.8 years. Participants in pre-frail (β = -0.18, 95% CI: -0.24, -0.13) and frail (β = -0.39, 95% CI: -0.48, -0.30) groups experienced an accelerated decline in MMSE score compared with the robust group. The PDI modified the above association, with corresponding associations with frailty being much more pronounced among participants with a lower PDI (frail vs. robust β = -0.44, 95% CI: -0.56, -0.32), compared with those with a higher PDI (frail vs. robust β = -0.27, 95% CI: -0.40, -0.13). In addition, A combination of frailty and a low PDI was strongly associated with a faster decline in MMSE score (β = -0.52, 95% CI: -0.63, -0.41).

Conclusion: Adherence to plant-based dietary patterns attenuates the association between frailty and cognitive decline. If the observed association is causal, promoting plant-based dietary patterns may be a strategy to reduce the effects of frailty on neurological health.