How does the Mediterranean diet associate with cognitive risk and functional ability in adults?

By Tarun Sai LomteDec 9 2022Reviewed by Aimee Molineux

A recent study published in Frontiers in Public Health evaluated the associations between adherence to the Mediterranean diet (MedDiet), cognitive risk, and functional ability in older Australian adults.

Aging is associated with the dysregulation of immunity, characterized by the upregulation of pro-inflammatory cytokines. Epidemiologic studies indicate that adherence to a plant-based diet might be protective against dementia and cognitive decline. Specifically, MedDiet adherence has been positively linked to healthy cognitive functioning. MedDiet has been promoted as one of the most nutritious diets to reduce chronic disease risk.

About the study

In the present study, researchers evaluated the associations of adhering to a MedDiet with functional status and the risk of cognitive impairment in older adults in Australia. Community-dwelling permanent Australian residents aged 60 or above, who were free from cognitive decline or dementia, were invited between February and May 2022 to participate in the study via social media platforms.

Survey links were disseminated weekly to participants using social media platforms. A self-administered 75-item questionnaire was used to evaluate the associations. The questionnaire had six sections and included validated tools such as the eight-item informant interview to differentiate aging and dementia (AD8), depression anxiety scale (DASS-21), Lawton’s instrumental activities of daily living (iADLs) scale, and the MedDiet adherence screener (MEDAS). In this study, the authors reported on the data from MEDAS, AD8, and Lawton’s iADLs.

The questionnaire also comprised closed- and open-ended questions on demographic characteristics. Functional ability was assessed using the modified Lawton’s iADL scale, comprising questions on instrumental activities such as shopping, housekeeping, food preparation, responsibility for medications, the ability to use a telephone and handle finances, laundry, and mode of transportation.

The AD8 dementia screening interview was used to assess cognitive function. MedDiet adherence was assessed using the 14-item MEDAS, which includes 12 questions assessing the main dietary elements of a conventional MedDiet and two on food consumption behaviors. Pearson’s correlation coefficients and uni- and multi-variable linear regression analyses were used to identify associations between MedDiet adherence, cognitive risk, and functional status.

Results

The online questionnaire was completed by 303 participants, including 205 females, 96 males, and two individuals of unspecified gender. Among these, 294 subjects completed all survey components and were included in the final analysis. Most participants could mobilize independently without requiring mobility aids. The entire sample had normal cognitive functioning and a high functional ability and independence, per the iADL and AD8 scores.

Seventy-nine participants were at risk of cognitive impairment. Sample t-tests revealed significant gender differences in functional ability and MEDAS scores. The cognitive risk was not significantly different between males and females. The entire sample showed moderate adherence to the MedDiet. Pearson’s correlation coefficients revealed that MedDiet adherence was weakly but positively associated with functional status and inversely associated with cognitive risk.

In uni- and multi-variable regression analyses, MedDiet adherence showed a positive association with functional ability, independent of sex, age, BMI, sleep duration, smoking status, physical activity duration, education status, and diabetes. Adherence to a MedDiet was inversely associated with cognitive risk, independent of covariates.

When MEDAS dietary elements were assessed individually, consumption of sugar-sweetened beverages and nut intake showed an inverse association with cognitive risk independent of covariates. Consumption of sugar-sweetened drinks and vegetable intake were positively associated with functional ability. The researchers repeated regression analyses among participants who were free from cognitive impairment (AD8 score of <2).

MedDiet adherence remained positively associated with functional ability independent of age, sex, and BMI. Nonetheless, the association was insignificant when controlling for other covariates (sleep and physical activity duration, smoking, diabetes, and education status). The sensitivity analyses indicated that MedDiet adherence was not associated with cognitive risk in those with an AD8 score of <2.

Conclusions

The study demonstrated a positive association of MedDiet adherence with functional ability and an inverse association with cognitive risk, independent of covariates. Notably, sensitivity analyses revealed that adherence to a MedDiet was no longer associated with cognitive risk in participants who were free from cognitive impairment.

Consumption of vegetables (two or more cups/day) and sugar-sweetened beverages (< 250 ml/day) was positively associated with functional ability. These findings corroborate the growing evidence on MedDiet for healthy physical and cognitive aging.