Associating Heart and Brain Health using MRI
The takeaway
Evidence suggests a relationship between heart and brain health. The authors identified associations between structural and functional traits of the heart and brain that share genetic signatures with cardiac and brain diseases.
What's the science?
Cardiovascular disease is often clinically associated with brain diseases, but the underlying genetic, structural, and functional connections between the heart and the brain remain unknown. Magnetic resonance imaging (MRI) has been used to identify structural and functional abnormalities that are associated with disease in individual organs, though few studies have analyzed MRI data from both the heart and the brain to find correlations between the two.
This week in Science, Zhao and colleagues used multiorgan MRI to examine the connections between heart MRI features and structural and functional patterns in the brain. They then used genome-wide association studies (GWAS) to correlate these findings with genetic variants associated with both heart MRI traits and brain diseases.
How did they do it?
The authors analyzed MRI data from >40,000 participants in the UK Biobank study. They identified 82 cardiac MRI traits that included measurements of the four cardiac chambers, the ascending and descending aortas, and wall thickness of different regions of the heart. A variety of brain MRI traits were also identified using imaging techniques that examine both structure and functional connectivity of different brain regions at rest and during specific tasks. Next the authors used statistical association and correlation analyses to explore associations between the identified traits.
The authors then performed GWASs to identify specific genetic variations associated with the cardiac MRI traits. They repeated the GWAS on several different datasets to confirm the associations in a wider population. Next, they completed association and colocalization studies on the significant genetic variants to determine whether the cardiac and brain MRI traits shared genetic signatures. Finally, they sought to determine a genetic causal relationship between the heart and brain by applying Mendelian Randomization to the 82 cardiac MRI traits and several brain-related clinical outcome databases.
What did they find?
The authors found 4193 significant associations between the 82 identified cardiac MRI traits and brain MRI traits such as cortical thickness, white matter microstructure, and volume of specific brain regions. Associations were also observed between cardiac MRI traits and the functional connectivity between certain brain networks. GWASs identified associations of 49 cardiac MRI traits at 80 genomic loci, which were found to be repeated across several datasets, indicating the generalizability of the findings across populations. They identified genetic variants that were shared across the cardiac and brain MRI traits that had been associated with diseases of the heart and brain. Mendelian randomization analysis revealed a causal relationship between genetic signals associated with heart traits and neuropsychiatric disorders.
What's the impact?
This study found associations between heart and brain MRI traits that shared common genetic signatures. These findings denote a causal relationship between heart and brain health. This suggests that early intervention and treatment of heart conditions may improve brain health outcomes.