Adherence to the Australian dietary guidelines is not associated with brain structure or cognitive function in older adults

Background: Cognitive dysfunction is common in older adults, particularly in those with type 2 diabetes (T2D). Higher adherence to the Dietary Guidelines for Americans is associated with better brain health. However, it is unclear if adherence to the Australian Dietary Guidelines (ADG) is associated with cognition or brain structure in older adults.

Objective: The aims of this study were to 1) examine the relation between adherence to the ADG, cognition, and brain MRI and 2) determine whether T2D modifies any associations.

Methods: The Cognition and Diabetes in Older Tasmanians Study is a cross-sectional study in 688 people (n = 343 with T2D) aged 55-90 y. A validated 80-item food-frequency questionnaire was used to assess dietary intake. Adherence to the 2013 ADG was estimated using the Dietary Guidelines Index (DGI). Cognitive function in multiple domains was assessed with a comprehensive battery of neuropsychological tests and brain structure with MRI. Multivariable linear models were used to assess the associations between DGI, cognitive z scores, and brain structure. Effect modification for T2D was examined with a DGI × T2D product term.

Results: The mean age of the sample was 69.9 y (SD: 7.4 y), with 57.1% men. The mean DGI was 54.8 (SD: 10.7; range: 24.1-84.6). No associations were observed between the Australian DGI and cognition or brain MRI measures. T2D did not modify any associations (P > 0.05).

Conclusions: This is the first study to investigate associations between adherence to the ADG and brain health in the older adults with and without T2D. Future prospective studies are required to clarify if there are long-term associations.