Intake of fruit and vegetables and the incident risk of cognitive disorders: A systematic review and meta-analysis of cohort studies

No quantitative assessment has been performed to specifically link the consumption of fruit and vegetables with the incident risk of cognitive disorders. We searched the PubMed and the Embase databases (both from the inception to June 13th, 2016) for records that report the intake of fruit and vegetables and the risk of developing cognitive disorders (Alzheimer's disease, dementia, and cognitive decline/ impairment). A generic inverse-variance method (random-effects model) was used to combine the relative risks (RRs) and 95% confidence intervals (CIs). To explore the potential sources of heterogeneity, we performed the subgroup and meta-regression analyses by pre-specified characteristics. We identified 6 cohorts involving a total of 21,175 participants. The pooled analysis showed that consumption of fruit and vegetables was inversely associated with the incident risk of cognitive disorders, and the pooled RR (95% CI) was 0.74 (0.62, 0.88), with evidence of significant heterogeneity (I-2 =68%). Furthermore, we found that the significant heterogeneity might be attributed to the ethnic difference. Further large prospective studies should be performed to quantify the potential dose-response patterns of fruit and/or vegetables intake and to explore the role of fruit or vegetables consumption separately on cognitive disorders in different populations.