Does the Mediterranean Diet Reduce Dementia Risk Over a 20-Year Period?

Following conventional dietary recommendations or a modified Mediterranean diet does not reduce the risk of developing dementia over a 20-year period, according to study findings published in Neurology.

In 2015, an estimated 47 million individuals had dementia worldwide. This figure is expected to triple over the next 3 decades. To mitigate progression to dementia, many studies have focused on finding potential modifiable risk factors. One potential modifiable factor is diet.

The Malmö Diet and Cancer study (MDCS) was a population-based, prospective cohort study which recruited adults in midlife who were living in Sweden between 1991 and 1996. Participants (N=28,025) answered questions about their dietary habits and their diet was scored for adherence to the conventional dietary recommendations using the Swedish dietary guidelines score (SDGS) and to the modified Mediterranean diet using the modified Mediterranean diet score (mMDS).

The primary outcome was risk for all-cause dementia on the basis of dietary habits. Secondary outcomes included progression to Alzheimer dementia and vascular dementia.

From baseline to December 2014 or death, 1943 individuals (6.9%) developed dementia and 26,082 did not. The individuals in the dementia and non-dementia cohorts were:

• Mean age, 64.3 (standard deviation [SD], 5.9) and 57.6 (SD, 7.5) years (P <.001),
• 61% and 61% were women,
• Body mass index (BMI) was 26.08 (SD, 3.96) and 25.72 (SD, 3.97) kg/m² (P <.001),
• 13.8% and 23.6% attended 13 or more years of education (P <.001), and
• Total energy intake was 9380 (SD, 2760) and 9540 (SD, 2730) kJ/day (P =.005), respectively.

For adherence to the conventional dietary recommendations, risk for all-cause dementia (adjusted hazard ratio [aHR], 0.99; 95% CI, 0.95-1.03), Alzheimer disease (AD) dementia (aHR, 0.99; 95% CI, 0.95-1.04), and vascular dementia (aHR, 1.00; 95% CI, 0.93-1.08) were not significantly related with SDGS. Stratified by level of adherence, individuals who had intermediate or high dietary adherence were not associated with lower risk for any dementia outcomes compared with those who had low dietary adherence.

Similarly, mMDS was not related with risk for all-cause dementia (aHR, 1.00; 95% CI, 0.96-1.04), AD dementia (aHR, 0.99; 95% CI, 0.94-1.04), or vascular dementia (aHR, 1.06; 95% CI, 0.98-1.15). No significant associations were observed between dementia outcomes among individuals with intermediate or high mMDS scores compared with those with low mMDS scores.

In sensitivity analyses, no significant outcomes were observed when using the Mediterranean Diet Score, when apolipoprotein E4 (ApoE) genotype was added to the models, or when cerebrospinal fluid (CSF) levels of amyloid-beta among a subset of participants (n=777) was added to the models.

This study may have been limited by the evaluation of diet, which was done at baseline via a 7-day food diary and a 1-hour interview.

These data did not support the notion that dietary habits from midlife affected risk for dementia at 20 years.

The researchers concluded that “Randomized controlled trials are needed to provide additional evidence regarding the potential role of diet in relation to AD pathology.”

Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.