title: Association of mediterranean diet with mild cognitive impairment and Alzheimer's disease: a systematic review and meta-analysis.
abstract: OBJECTIVE
  To conduct a systematic review of all studies to determine whether there is an association between the Mediterranean diet (MeDi) and cognitive impairment.
  
  
  METHODS
  We conducted a comprehensive search of the major databases and hand-searched proceedings of major neurology, psychiatry, and dementia conferences through November 2012. Prospective cohort studies examining the MeDi with longitudinal follow-up of at least 1 year and reporting cognitive outcomes (mild cognitive impairment [MCI] or Alzheimer's disease [AD]) were included. The effect size was estimated as hazard-ratio (HR) with 95% confidence intervals (CIs) using the random-effects model. Heterogeneity was assessed using Cochran's Q-test and I2-statistic.
  
  
  RESULTS
  Out of the 664 studies screened, five studies met eligibility criteria. Higher adherence to the MeDi was associated with reduced risk of MCI and AD. The subjects in the highest MeDi tertile had 33% less risk (adjusted HR = 0.67; 95% CI, 0.55-0.81; p < 0.0001) of cognitive impairment (MCI or AD) as compared to the lowest MeDi score tertile. Among cognitively normal individuals, higher adherence to the MeDi was associated with a reduced risk of MCI (HR = 0.73; 95% CI, 0.56-0.96; p = 0.02) and AD (HR = 0.64; 95% CI, 0.46-0.89; p = 0.007). There was no significant heterogeneity in the analyses.
  
  
  CONCLUSIONS
  While the overall number of studies is small, pooled results suggest that a higher adherence to the MeDi is associated with a reduced risk of developing MCI and AD, and a reduced risk of progressing from MCI to AD. Further prospective-cohort studies with longer follow-up and randomized controlled trials are warranted to consolidate the evidence. Systematic review registration number: PROSPERO 2013: CRD42013003868.
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN, USA Department of Clinical Neuroscience, University of North Dakota School of Medicine and Health Sciences, Fargo, ND, USA.
authors.forename: Balwinder
authors.initials: B
authors.lastname: Singh
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Ajay K
authors.initials: AK
authors.lastname: Parsaik
authors.affiliation: Division of Epidemiology, Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Mielke
authors.affiliation: Mayo Medical Libraries, Mayo Clinic, Rochester, MN, USA.
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Erwin
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Knopman
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN, USA Division of Epidemiology, Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA.
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Petersen
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN, USA Division of Epidemiology, Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA.
authors.forename: Rosebud O
authors.initials: RO
authors.lastname: Roberts
mesh_terms: D000544:Alzheimer Disease / Q000453:epidemiology*; D060825:Cognitive Dysfunction / Q000453:epidemiology*; D038441:Diet, Mediterranean; D018450:Disease Progression; D006801:Humans; D012306:Risk
keywords: Alzheimer's disease; Mediterranean diet; meta-analysis; mild cognitive impairment; systematic review