Association of Mediterranean Diet with Mild Cognitive Impairment and Alzheimer's Disease: A Systematic Review and Meta-Analysis

Abstract

Background/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.

Extra-virgin olive oil ameliorates cognition and neuropathology of the 3xTg mice: role of autophagy

“…Epidemiological and clinical studies have consistently indicated that higher adherence to the Mediterranean diet is associated with a reduced risk of developing mild cognitive impairment and AD, and a reduced risk of progressing from mild cognitive impairment to AD 4, 5. Among the different nutrients that characterize the Mediterranean diet, a lot of attention has been focused on the extra‐virgin olive oil (EVOO) daily intake, which is estimated to be quite high in the Mediterranean area populations compared with other geographical regions around the world 6, 7…”

Dietary patterns and whole grain cereals in the Scandinavian countries – differences and similarities. The HELGA project

“…Among theoretically (a priori) defined patterns, the Mediterranean diet has been associated with positive health outcomes in many studies (10)(11)(12)(13)(14) . Similarly, a Nordic Food Index has been suggested for the Nordic countries.…”

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“…Because MCI seems to be part of the continuum from normal aging to development of Alzheimer's disease and other dementias, identifying dietary patterns that can help delay this progression is important (114,132). Dietary approaches that include grains and whole grains and their beneficial components as part of a balanced pattern appear to be associated with reduced risk (not with increased risk as has been alleged by some) and delayed onset of MCI, Alzheimer's disease, and Parkinson's disease.…”

“…Since the first published studies showing the cognitive benefits of adherence to the Mediterranean Diet, studies from New York, rural Utah, and Australia have shown that greater compliance with such dietary patterns from the middle decades of life and beyond is associated with reduced risk for MCI and Alzheimer's disease and slower progression of the disease (89,90,93,97,(106)(107)(108)(109)(110)(111)(112)(113)(114)(115)(116)(117). Similarly, high adherence to DASH and other balanced dietary patterns that emphasize intake of fruits, vegetables, cereals, and whole grains have also been associated with a lower likelihood of developing Alzheimer's disease (90,97,110,115).…”