Dietary Patterns Are Not Associated with Brain Atrophy or Cerebral Small Vessel Disease in Older Adults with and without Type 2 Diabetes

Background: Unhealthy dietary patterns (DPs) are associated with poorer cognition, but few studies have investigated the underlying brain structural mechanisms. Objective: We aimed to examine the relations between DPs, brain structure, and cognition in older people with and without type 2 diabetes. Methods: This cross-sectional study consisted of a sample of people with (n = 343) and without type 2 diabetes (n = 346) aged 55-90 y. The 80-item Cancer Council of Victoria FFQ was used to assess dietary intake. Two DPs (prudent and traditional) for people with type 2 diabetes and 3 DPs (prudent, traditional, and Western) for those without type 2 diabetes were derived using principal component analysis. Neuropsychological tests assessed 6 cognitive domains. Brain MRI was performed to obtain gray, white matter, and hippocampal volumes and markers of small vessel disease (microbleeds, infarcts, and white matter hyperintensities). Multivariable linear regression was used to assess the cross-sectional associations between DPs, brain MRI, and cognitive variables. Results: For those without type 2 diabetes, higher adherence to the Western DP was associated with lower gray matter volume (beta = -3.03 95% CI: -5.67, -0.38; P = 0.03). The addition of a cardiovascular risk score, mood, and physical activity weakened associations such that they were no longer significant (beta = -1.97 (95% CI: -4.68, 0.74) P = 0.15) for the Western DP. There were no significant associations for the other DPs in people with and without type 2 diabetes. Conclusions: In this cross-sectional study, DPs were not independently associated with brain structure in people with or without type 2 diabetes. Future prospective studies are needed to clarify the role of vascular risk factors on associations between DPs and brain health.