Associations between plant-based diets and cardiovascular disease, frailty, and cognitive dysfunction in middle and old age: a systematic review and meta-analysis of cohort studies

Abstract

Background Evidence suggested that plant-based diets are associated with multiple health outcomes. In a review of previous pooled studies, the lack of a standardized definition of plant-based diet has led to conflicting evidence linking plant-based diet to the health of middle-aged and elderly people. Methods and findings Searches were performed on PubMed, Embase, Cochrane Library and Web of Science databases from inception until July 10, 2024. We included studies that examined the association between standardized healthy plant-based Diet score (hPDI), unhealthy plant-based diet score (uPDI), and cardiovascular disease (CVD), cardiovascular mortality (CVD mortality), frailty, and cognitive dysfunction. The dose-response relationship between healthy plant diet score, unhealthy plant diet score and CVD and frailty was further discussed by dose-response analysis. Statistical analysis was performed using an inverse variance random effects model and results are reported as risk ratios (RRs) with 95% confidence intervals (CIs) by combining the most adjusted RR, odds ratios (ORs) and hazard ratios (HRs) under the rare outcome assumption. Finally, we included 25 cohort studies that showed that higher hPDI was associated with a lower risk of CVD (RR=0.81, 95%CI 0.71-0.93), CVD mortality (RR=0.83, 95%CI 0.75-0.90), CHD (RR=0.79, 95%CI 0.70-0.88), stroke (RR=0.91, 95%CI 0.86-0.96), ischemic stroke (RR=0.86, 95%CI 0.79-0.94), cognitive dysfunction (RR=0.75, 95%CI 0.66-0.84) and frailty (RR=0.72, 95%CI 0.60-0.86). Higher uPDI score was associated with an increased risk of CVD (RR=1.16, 95%CI 1.09-1.24), CVD mortality (RR=1.14, 95%CI 1.05-1.23), frailty (RR=1.52, 95%CI 1.10-2.08) and cognitive dysfunction (RR=1.24, 95%CI 1.11-1.38). The dose-response relationship with CVD and frailty showed that the risk of CVD and frailty decreased with increasing intake of hPDI. In contrast, the increased intake of uPDI was associated with an increased risk of CVD and frailty. Conclusions Our study suggested that hPDI was beneficial for most middle-aged and elderly health outcomes, except for hemorrhagic stroke. This demonstrated the potential benefits of hPDI.