The relationship between dietary patterns and cognitive health among older adults

Abstract

Dementia and cognitive decline, most commonly secondary to Alzheimer’s disease, affects over 50 million people globally, placing a significant financial and social burden on patients, carers and health care systems. As life expectancy is increasing and the population is ageing, the number of people living with dementia has been estimated to triple by 2050. No effective pharmaceutical treatment for most causes of dementia or cognitive decline is available so far. Prevention or delay onset holds more promise.

Among modifiable factors, diet may be a promising strategy to postpone, slow or prevent cognitive decline and reduce the risk of dementia. The overall aim of this thesis is to answer the important question as to whether, and how effective, different types of dietary patterns and related food groups are in protecting against neurocognitive decline in older adults?

This thesis presents a comprehensive systematic review by collating and evaluating the evidence from all human studies of RCTs and prospective cohorts conducted on a variety of dietary patterns and the outcome of cognitive function and/or dementia; examines cross-sectional relationship and longitudinal associations between dietary patterns and key food components within dietary patterns, and cognitive function and cognitive decline with ageing; examines dietary quality among Australian older adults and investigates association between diet quality indices and cognitive performance, using data from the Sydney Memory and Ageing Study, which is a well-characterized Australian ageing cohort. Finally, recommendations for future research are provided.

Overall, this thesis reveals that greater adherence to healthy dietary patterns which are plant based and rich in mono-/poly unsaturated fatty acids, were proven to be cross-sectionally associated with better cognition; and intake of legumes and nuts were positively linked both cross-sectionally and longitudinally to better performance and less decline in multiple cognition domains and global cognition. By contrast, a westernised diet was linked to overall poorer global function over years. No association between adherence to Australian Dietary Guidelines and cognitive performance was found, and future research is needed to provide further evidence and support specific dietary guidelines for neurocognitive health among Australian older adults.