Adherence to Mediterranean diet and risk of developing cognitive disorders: An updated systematic review and meta-analysis of prospective cohort studies

Abstract

Recent articles have presented inconsistent findings on the impact of Mediterranean diet in the occurrence of cognitive disorders; therefore, we performed an updated systematic review and meta-analysis to evaluate the potential association and dose-response pattern with accumulating evidence. We searched the PubMed and the Embase for the records relevant to this topic. A generic inverse-variance method was used to pool the outcome data for continuous variable, and categories of high vs. low, median vs. low of Mediterranean diet score with a random-effects model. Generalized least-squares trend estimation model was used to estimate the potential dose-response patterns of Mediterranean diet score on incident cognitive disorders. We identified 9 cohort studies involving 34,168 participants. Compared with the lowest category, the pooled analysis showed that the highest Mediterranean diet score was inversely associated with the developing of cognitive disorders, and the pooled RR (95% CI) was 0.79 (0.70, 0.90). Mediterranean diet score of the median category was not significantly associated with cognitive disorders. Dose-response analysis indicated a trend of an approximately linear relationship of the Mediterranean diet score with the incident risk of cognitive disorders. Further studies of randomized controlled trials are warranted to confirm the observed association in different populations.

Figure 1. Flow diagram of the articles included in the present study.

Figure 2. Forest plot of relative risks (RRs) and 95% confidence intervals (CIs) for the association between Mediterranean diet score (High vs. Low) and the incident risk of cognitive disorders by outcome type.

MCI, mild cognitive impairment; AD, Alzheimer’s disease.

Figure 3. Forest plot of relative risks (RRs) and 95% confidence intervals (CIs) for the association between Mediterranean diet score (Median vs. Low) and the incident risk of cognitive disorders by outcome type.

MCI, mild cognitive impairment; AD, Alzheimer’s disease.

Figure 4. Forest plot of relative risks (RRs) and 95% confidence intervals (CIs) for the association between Mediterranean diet score (Continuous) and the incident risk of cognitive disorders by outcome type.

MCI, mild cognitive impairment; AD, Alzheimer’s disease.

Figure 5. Dose-response association between Mediterranean diet score and cognitive disorders.

(a) Mild cognitive impairment, (b) Alzheimer’s disease, (c) Dementia, (d) Cognitive disorders. Solid line, best-fitting restricted cubic spine; dotted line, 95% CI.