A large UK cohort study found that adults with healthier diets and lower waist-to-hip ratios during midlife had associations with better brain connectivity and cognitive performance later in life.
The cohort study, published in JAMA Network Open, included magnetic resonance imaging (MRI) and cognitive testing at a mean participant age of 70 years.
Researchers analyzed data from 512 individuals in the diet cohort and 664 in the waist-to-hip ratio (WHR) cohort from the Whitehall II Study. Diet quality was assessed three times over 11 years, and WHR was measured five times over 21 years, beginning in midlife (mean baseline age, 48 years). Brain imaging and cognitive testing were conducted between 2012 and 2016.
Diet quality was measured using the Alternative Healthy Eating Index–2010 (AHEI-2010). The mean AHEI-2010 score at baseline was approximately 55 of a possible 110 points, indicating suboptimal diet quality. Although group-level diet quality remained stable, individual improvements over time were associated with better brain outcomes.
Higher AHEI-2010 scores in midlife were associated with stronger functional connectivity between the hippocampus and brain regions including the occipital lobe and cerebellum. Improvements in diet over time were associated with greater white matter integrity, indicated by increased fractional anisotropy (FA) and decreased mean diffusivity (MD) and axial diffusivity (AD). AHEI-2010 slope was significantly associated with FA and AD in the fornix.
In contrast, higher midlife WHR was associated with lower white matter integrity in tracts such as the cingulum and inferior longitudinal fasciculus. Specifically, higher WHR was linked to increased MD in 26.4% of white matter tracts, increased radial diffusivity in 23.1%, and lower FA in 4.9%.
Cognitively, higher midlife WHR was associated with poorer performance on tests of verbal episodic memory, digit span, semantic fluency, digit coding, and trail making. Mediation analysis showed that 15% of the association between WHR and digit span performance and 16% of the association with digit coding performance were mediated by global FA.
There was no association between WHR and hippocampal functional connectivity, and improvements in diet quality were not significantly associated with overall cognitive scores after correction for multiple comparisons.
The cohort was predominantly male (approximately 80%) and largely composed of White British individuals with high educational attainment, which may limit the generalizability of the findings.
The authors suggest that interventions to improve diet and manage central obesity may be most effective when implemented between ages 48 and 70 years.
Conflict of interest disclosures are available in the original article.