Dementia prevention is a global public health priority due to the high societal cost of this condition. Dementia incidence can be reduced by identifying and targeting modifiable risk factors through personalized or public health interventions. One such risk factor is diet which can be targeted for dementia prevention and risk reduction. Studies have reported healthier dietary patterns, such as the Mediterranean diet (MedDiet), to be an important strategy for reducing dementia risk. Recent reviews have indicated that higher adherence to the MedDiet was associated with reduced cognitive decline. However, additional investigations are required since most previous studies were conducted in small cohorts with limited dementia cases.

A healthy diet can also reduce the individual genetic risk for dementia. However, previous studies that analyzed gene-diet interactions are limited, and their results are inconsistent. Polygenic risk scores have been reported to be important for predicting all-cause dementia and can be used for the in-depth exploration of potential gene-diet interactions.

A new study in the journal BMC Medicine aimed to analyze the association between dementia incidence and MedDiet adherence as well as assess the interaction between genetic risk and diet for dementia.

Study: Mediterranean diet adherence is associated with lower dementia risk, independent of genetic predisposition: findings from the UK Biobank prospective cohort study. Image Credit: Marian Weyo / Shutterstock

About the study

The study involved recruiting participants who were included in the UK Biobank study and were 60 years of age or above, self-reported to be British, Irish, or other white, and had accurate genetic and dietary data. Dietary assessment was done using the Oxford WebQ, a web-based dietary assessment tool. MedDiet adherence was quantified using the MedDiet PYRAMID score and the MedDiet Adherence Screener (MEDAS) score. The MEDAS is a 14-point score widely used in observational studies and trials, while the PYRAMID score is a 15-point widely used in epidemiological studies.

Polygenic risk scores were used for the estimation of the genetic risk of dementia. All-cause incident dementia cases were confirmed using hospital inpatient records and death registries. The International Classification of Diseases (ICD) coding system was used for recording the diagnoses. Sensitivity analyses were carried out to assess the robustness of associations between dementia incidence and MedDiet adherence.

Study findings

The results indicated that a total of 882 cases of incident all-cause dementia were included in the study. Participants with a higher MedDiet adherence as per the MEDAS continuous score were reported to be primarily female, had a BMI within a healthy range, were more physically active, and had a higher educational level. The mean MEDAS continuous score was reported to be  6.1±1.7, and the PYRAMID score was 7.5±1.8.

Higher adherence to the MedDiet was reported to be associated with 4.2 to 6.9 percent lower dementia risk for the MEDAS continuous and PYRAMID scores. Additionally, a higher polygenic risk score was reported to be associated with greater dementia risk. The results from the sensitivity analysis also confirmed that higher MedDiet adherence was associated with lower dementia incidence.

Therefore, the current study demonstrated that higher adherence to a MedDiet was associated with a lower risk of dementia. However, the evidence for interaction with genetic risk was unclear. This study suggests the importance of dietary interventions in the development of dementia prevention strategies in the future, irrespective of genetic predisposition.

Limitations

The first limitation of the study is that its observational design prevents it from drawing causal inferences. Second, lower MedDiet adherence can be a consequence and not cause dementia. Third, the calculated MedDiet scores might not fully represent the participant’s usual dietary intake. Fourth, the number of dementia cases was obtained from hospital records and death registries only, which could miss a few cases. Finally, UK Biobank participants were of higher socioeconomic status and healthier as compared to the general UK population.

Journal reference:

• Shannon, O.M. et al. (2023). Mediterranean diet adherence is associated with lower dementia risk, independent of genetic predisposition: fndings from the UK Biobank prospective cohort study. BMC Medicine. doi: https://doi.org/10.1186/s12916-023-02772-3. https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-023-02772-3