Effectiveness and feasibility of a theory-informed intervention to improve Mediterranean diet adherence, physical activity and cognition in older adults at risk of dementia: the MedEx-UK randomised controlled trial

Abstract

Background: Despite an urgent need for multi-domain lifestyle interventions to reduce dementia risk, there is a lack of interventions which are informed by theory- and evidence-based behaviour change strategies, and no interventions in this domain have investigated the feasibility or effectiveness of behaviour change maintenance. We tested the feasibility, acceptability and cognitive effects of a personalised theory-based 24-week intervention to improve Mediterranean diet (MD) adherence alone, or in combination with physical activity (PA), in older-adults at risk of dementia, defined using a cardiovascular risk score.

Methods: Participants (n = 104, 74% female, 57-76 years) were randomised to three parallel intervention arms: (1) control, (2) MD, or (3) MD + PA for 24 weeks and invited to an optional 24-week follow-up period with no active intervention. Behaviour change was supported using personalised targets, a web-based intervention, group sessions and food provision. The primary outcome was behaviour change (MD adherence and PA levels), and the secondary outcomes included feasibility and acceptability, cognitive function, cardiometabolic health (BMI and 24-h ambulatory blood pressure) and process measures.

Results: The intervention was feasible and acceptable with the intended number of participants completing the study. Participant engagement with group sessions and food provision components was high. There was improved MD adherence in the two MD groups compared with control at 24 weeks (3.7 points on a 14-point scale (95% CI 2.9, 4.5) and 48 weeks (2.7 points (95% CI 1.6, 3.7)). The intervention did not significantly change objectively measured PA. Improvements in general cognition (0.22 (95% CI 0.05, 0.35), memory (0.31 (95% CI 0.10, 0.51) and select cardiovascular outcomes captured as underpinning physiological mechanisms were observed in the MD groups at 24 weeks.

Conclusions: The intervention was successful in initiating and maintaining dietary behaviour change for up to 12 months which resulted in cognitive benefits. It provides a framework for future complex behaviour change interventions with a range of health and well-being endpoints.

Trial registration: ClinicalTrials.gov NCT03673722.

Keywords: Behaviour change; Dementia; Mediterranean diet; Physical activity; RCT.

Fig. 1

Mediterranean Diet Adherence Screener (MEDAS) score by intervention group at baseline and 24 and 48 weeks calculated by questionnaire and 24-h recall. Values represent unadjusted means (SD) from MEDAS questionnaire (A) and 24-h recall (B). P-value for group and contrast 1 (control v. (MD + MD + PA)) * < 0.01 or ** < 0.05 at relevant time point compared to baseline, calculated using ANCOVA (adjusted for baseline value, study site and baseline BMI). P-values for contrast 2 (MD v. MD + PA) were non-significant at all timepoints compared to baseline as were all contrasts comparing values at 48 to 24 weeks. Participant numbers at 48 weeks were n = 20 MD + PA, n = 22 MD, n = 21 control for questionnaire data and n = 17 MD + PA, n = 17 MD, n = 12 control for 24 = hr recall data. MD, Mediterranean diet; MEDAS, Mediterranean Diet Adherence Screener; PA, physical activity

Fig. 2

Proportion of participants adapting to meet the criteria for individual Mediterranean Diet Adherence Screener components at 24 weeks by intervention group in 86 MedEx-UK participants. Bars represent the percentage of participants who met the criteria at 24 weeks but not at baseline according to the questionnaire data. Only participants with complete data for all components were included (n = 86). Missing bars indicate the percentage of participants was zero

Fig. 3

Cognitive summary scores by intervention group at baseline and 24 and 48 weeks. Values represent unadjusted means (SD) for general cognition (A), processing speed (B), executive function (C) and executive function (D). * P-value < 0.01 for group and contrast 1 (control v. (MD and MD + PA)) at relevant time point compared to baseline, calculated using ANCOVA (adjusted for baseline value, study site baseline age, and years of education). P-values for contrast 2 (MD v. MD + PA) were non-significant at all timepoints compared to baseline as were all contrasts comparing values at 48 to 24 weeks. Missing data at 48 weeks were general cognition (MD + PA n = 7, MD n = 3, control n = 8), processing (MD + PA n = 5, MD n = 5, control n = 9), executive function (MD + PA n = 6, MD n = 10, control n = 11) and executive function (MD + PA n = 11, MD n = 9, control n = 8). Individual test scores were converted to Z scores standardised on baseline grand mean and standard deviation with response time variables reversed by [Z * − 1], so a higher time indicates a better outcome. Individual Z scores test scores were mean aggregated into summary scores for the following: Processing speed [Digit symbol substitution (total correct); Trail Making Test (A, seconds)]; Executive Function [Controlled Oral Word Association Test (total); Categorical verbal fluency test (total); Trail Making Test (B-A, seconds); Wechsler Memory Digit Span (backwards, total)] and Memory [Verbal paired immediate (total); Visual paired immediate (total); Verbal paired delayed (total); Visual paired delayed (total); Rey Auditory Verbal Learning Test (immediate); Rey Auditory Verbal Learning Test (recall)]. A general cognition score was calculated using all Processing speed, Executive function and Memory tests. MD, Mediterranean diet; MEDAS, Mediterranean Diet Adherence Screener; PA, physical activity. Full data is presented in Additional file 1: Table S7