Adherence To A Healthy Diet And General Functional Performance Of Dutch Older Adults In The Nu-Age Dietary Intervention Study

ABSTRACT

Background: A summated score is a useful way to capture the different measuring constructs of cognitive functioning, physical functioning and quality of life in healthy ageing. Observational studies and randomized controlled trials have demonstrated that high quality diets improve general health and well-being. The NU-AGE diet quality index was developed with the aim of ensuring healthy ageing for European older adults.

Objective: The primary aim of this study was to develop a summated general functional performance score incorporating the cognitive functioning, physical functioning and quality of life of older adults. Additionally, we studied the association between adherence to the NU-AGE diet and the summated general functional performance score.

Method: Our study design was cross-sectional using baseline data of Dutch participants in the NU-AGE dietary intervention study. Participants included 252 (55.5% female) older adults recruited in Wageningen and surroundings. Cognitive functioning was assessed with the CERAD Neuropsychological Assessment Battery (NAB), domain specific tests and depression. Physical functioning was assessed with handgrip strength, Short Physical Performance Battery (SPPB), 6 minutes walking test (6MWT), instrumental activities of daily living (IADL), activities of daily living (ADL) and physical activity. Participants completed questionnaires to measure quality of life, socio- demography and medical history. We used Principal Component Analysis (PCA) with orthogonal varimax rotation to create a summated general functional performance z-score. Dietary intake was assessed with a consecutive 7-day food record. Adherence to a healthy diet was defined using the NU-AGE Diet Score (NDS) which consists of 7 adequacy and 4 moderation components. The NDS is an a priori diet quality index; scoring is continuous with a maximum score of 10 for each component and a total score ranging from zero (no adherence) to 110 (complete adherence). Logistic regression models were fitted to analyse the association between adherence to the NDS and the summated general functional performance z-score. Data analysis was done using SAS 9.3.

Results: The Cronbach measure of reliability for our summated general functional performance z- score was 0.78. The model adjusted for main confounders such as age, gender, lifestyle (smoking status, body mass index, energy intake), presence of chronic disease and socio-economic factors (education and financial status) showed that compared to participants with a low NDS adherence, those with moderate adherence were significantly more likely to have a high summated general functional performance z-score (OR 3.62, 95%CI: 1.75-7.50) whereas those with high NDS adherence were insignificantly more likely (OR 1.43, 95%CI: 0.69-2.95) to have a high summated general functional performance z-score; P-trend=0.16.

Conclusion: The summated general functional performance z-score had a good reliability and thus some key tests of cognitive functioning, physical functioning and quality of life may provide a valid combined measure of cognitive functioning, physical functioning and quality of life in epidemiological studies. In this cross-sectional study of Dutch older adults, moderate adherence to the NDS was significantly associated with better summated general functional performance, whereas high adherence was not.