Molecular Psychiatry (2015) 20, 860–866 © 2015 Macmillan Publishers Limited All rights reserved 1359-4184/15 www.nature.com/mp ORIGINAL ARTICLE Dietary patterns and cognitive decline in an Australian study of ageing SL Gardener1,2, SR Rainey-Smith1,2, MB Barnes3, HR Sohrabi1,2, M Weinborn1,2,4, YY Lim5, K Harrington5, K Taddei1,2,YGu6,7, A Rembach5, C Szoeke5, KA Ellis5,8,9, CL Masters5, SL Macaulay10, CC Rowe11, D Ames8,9, JB Keogh12, N Scarmeas6,7,13,14 and RN Martins1,2 for the AIBL Research Group15 The aim of this paper was to investigate the association of three well-recognised dietary patterns with cognitive change over a 3-year period. Five hundred and twenty-seven healthy participants from the Australian Imaging, Biomarkers and Lifestyle study of ageing completed the Cancer Council of Victoria food frequency questionnaire at baseline and underwent a comprehensive neuropsychological assessment at baseline, 18 and 36 months follow-up. Individual neuropsychological test scores were used to construct composite scores for six cognitive domains and a global cognitive score. Based on self-reported consumption, scores for three dietary patterns, (1) Australian-style Mediterranean diet (AusMeDi), (2) western diet and (3) prudent diet were generated for each individual. Linear mixed model analyses were conducted to examine the relationship between diet scores and cognitive change in each cognitive domain and for the global score. Higher baseline adherence to the AusMeDi was associated with better performance in the executive function cognitive domain after 36 months in apolipoprotein E (APOE) ε4 allele carriers (Po0.01). Higher baseline western diet adherence was associated with greater cognitive decline after 36 months in the visuospatial cognitive domain in APOE ε4 allele non-carriers (Po0.01). All other results were not significant. Our findings in this well-characterised Australian cohort indicate that adherence to a healthy diet is important to reduce risk for cognitive decline, with the converse being true for the western diet. Executive function and visuospatial functioning appear to be particularly susceptible to the influence of diet. Molecular Psychiatry (2015) 20, 860–866; doi:10.1038/mp.2014.79; published online 29 July 2014 INTRODUCTION a healthy diet and slower cognitive decline.3–9 By contrast, studies Improved healthcare and nutrition are contributing significantly to have also concluded that higher consumption of a healthy dietary – increased life expectancy, subsequently increasing the prevalence pattern is not protective against cognitive decline.10 13 These of age-related onset diseases, particularly Alzheimer’s disease previous studies have limitations, most notably, lack of compre- (AD). Cognitive decline is the progressive loss of cognitive funct- hensive cognitive testing whereby multiple cognitive domains are – – ions, including memory, and may lead to dementia, of which AD is assessed.3,7 9,11 13 There is a need for further longitudinal investi- the most common type.1 While there is no cure or effective treat- gation in highly characterised ageing cohorts. ment for AD, early intervention prevention programs hold consi- The aim of our study was to investigate the individual derable promise. Following particular dietary patterns represents association of three dietary patterns; (1) Australian-style Mediter- 14 one potential intervention strategy that is accessible to all. ranean diet (AusMeDi; ), (2) western diet and (3) prudent diet Individual diets contain both nutrient and non-nutrient sub- (a ‘healthy’ dietary pattern), with cognitive change over 3 years, stances rather than single foods. It may therefore be more useful assessed using a comprehensive neuropsychological battery. to examine indices of food and nutrient intake that express several This was investigated in a well-characterised, Australian elderly related aspects of diet concurrently rather than focus on con- cohort drawn from the larger Australian Imaging, Biomarkers sumption of single nutrients.2 and Lifestyle study of ageing (AIBL;15). The AusMeDi was Results from previous studies on the association between dietary constructed using an ‘a priori’ method and the western and patterns and future cognitive decline are inconsistent. Several prudent diet patterns constructed by factor analysis; an ‘a studies have shown a positive relationship between adherence to posteriori’ method. 1Centre of Excellence for Alzheimer's disease Research and Care, School of Medical Sciences, Edith Cowan University, Joondalup, WA, Australia; 2Sir James McCusker Alzheimer's Disease Research Unit (Hollywood Private Hospital), Perth, WA, Australia; 3CSIRO Computational Informatics, Glen Osmond, SA, Australia; 4School of Psychology, University of Western Australia, Crawley, WA, Australia; 5The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC, Australia; 6Taub Institute for Research of Alzheimer’s Disease and the Ageing Brain, Columbia University, New York, NY, USA; 7Gertrude H. Sergievsky Centre, Columbia University, New York, NY, USA; 8National Ageing Research Institute, Parkville, VIC, Australia; 9Academic Unit for Psychiatry of Old Age, St Vincent’s Health, Department of Psychiatry, The University of Melbourne, Kew, VIC, Australia; 10CSIRO Preventative Health Flagship, CMSE Parkville, VIC, Australia; 11Department of Nuclear Medicine and Centre for PET, Austin Health, Heidelberg, VIC, Australia; 12School of Pharmacy and Medical Sciences and Sansom Institute for Health Research, Division of Health Sciences, University of South Australia, Adelaide, SA, Australia; 13Department of Neurology, Columbia University College of Physicians and Surgeons, New York, NY, USA and 14Department of Social Medicine, Psychiatry, and Neurology, National and Kapodistrian University of Athens, Athens, Greece. Correspondence: Professor RN Martins, Centre of Excellence for Alzheimer's disease Research and Care, School of Medical Sciences, Edith Cowan University, 270 Joondalup Drive, Joondalup, 6027 WA, Australia. E-mail: [email protected] 15A full list of the AIBL investigators is available at www.aibl.csiro.au Received 31 October 2013; revised 17 June 2014; accepted 18 June 2014; published online 29 July 2014 Dietary patterns and cognitive decline SL Gardener et al 861 MATERIALS AND METHODS group was summed to derive the 33 groups for each individual. Factor Participants analysis (principle components) was conducted to derive dietary patterns.29 Food groups were entered as weight in grams per day. The This report describes data from 527 healthy control (cognitively ‘normal’) participants taken from the AIBL study15 who completed the Cancer factors were rotated by a varimax procedure resulting in non-correlated Council of Victoria food frequency questionnaire (CCVFFQ;16) at baseline. factors, to facilitate factor interpretability. In determining number of factors to retain, we considered components with an eigenvalue 41.25, Scree The AIBL study is a longitudinal study of 1112 volunteers including healthy 30 controls, those with mild cognitive impairment (MCI), and AD who are tests and interpretability. A cut-off of 0.20 was used to determine factor being assessed for prospective research into ageing and AD. MCI and AD loadings included in each pattern, and two major patterns were extracted, participants were excluded from this analysis as we are using a food labelled western pattern and prudent pattern; Table 1 shows factor frequency questionnaire that requires estimations of food intake over the loadings for these patterns. The dietary pattern score was constructed by previous year, and there is a potential for mis-classification due to limited summing intakes of the food groups weighted by factor loadings. accuracy in estimations. All AIBL volunteers were aged 60 years and above at baseline, and excluded if they had a history of non-AD dementia, Statistical analysis schizophrenia, bipolar disorder, significant current depression, Parkinson’s disease, cancer (other than basal cell skin carcinoma) within the last 2 All statistical analyses were performed using R version 3.0.1 (R Foundation years, symptomatic stroke, insulin-dependent diabetes, uncontrolled for Statistical Computing, Vienna, Austria). A P-value of 0.01 or smaller fi diabetes mellitus or current regular alcohol use exceeding two standard determined a signi cant result to balance the risk of type I and type II drinks per day for women or four per day for men. Further details errors, due to the large number of statistical tests performed. regarding recruitment, assessment, inclusion and exclusion criteria are Means, standard deviations and percentages are provided for the entire fi ε described in Ellis et al.15 The AIBL study is approved by the institutional cohort as well as following strati cation by APOE 4 allele carrier status. 2 ethics committees of Austin Health, St Vincent’s Health, Hollywood Private Independent samples t-tests and χ -analyses were conducted to evaluate Hospital and Edith Cowan University.15 group differences as appropriate. A series of repeated measures linear mixed model analyses (using maximum likelihood estimation and an unstructured covariance matrix) Cognitive assessments were conducted to examine the relationship between baseline diet score A comprehensive neuropsychological battery of well-validated measures and time (baseline, 18 and 36 month follow-up) with respect to cognitive was administered according to standard protocols (described