Abstract

Background: It is unclear how changes in plant-based dietary quality are linked to subsequent risk of cognitive impairment. This study aims to evaluate this relationship using data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS).

Methods: A total of 6662 participants free of cognitive impairment in 2008 were included and followed up to 2018. Plant-based dietary quality was assessed by three indices: overall plant-based diet index (PDI), healthful plant-based diet index (hPDI), and unhealthful plant-based diet index (uPDI). Changes in plant-based diet quality from 2008 to 2011 were classified into quintiles. We assessed incident cognitive impairment (from 2011 to 2018) by using the Mini-Mental State Examination (MMSE). Cox proportional-hazards models were performed.

Results: We recorded 1571 incident cases of cognitive impairment during a median of 10 years of follow-up. Compared with participants whose plant-based diet had no change or was relatively stable over three years, the full-adjusted hazard ratios (HRs) with 95% confidence intervals (CI) for cognitive impairment were 0.77 (0.64, 0.93), 0.72 (0.60, 0.86), and 1.50 (1.27, 1.77) among participants with a large increase in PDI, hPDI, and uPDI, respectively. The HRs with 95% CI were 1.22 (1.02, 1.44), 1.30 (1.11, 1.54), and 0.80 (0.67, 0.96) among participants with a large decrease in PDI, hPDI, and uPDI, respectively. Every 10-point increase in PDI and hPDI was associated with 26% and 30% lower risk of cognitive impairment, while every 10-point increase in uPDI was associated with 36% higher risk.

Conclusions: Older adults with increased adherence to an overall plant-based diet and a healthful plant-based diet over three years have a lower risk of cognitive impairment, while those with increased adherence to an unhealthy plant-based diet had a higher risk of cognitive impairment.