Background Existing work, using indirect health measures, suggests independent links between brain and heart health within disease cohorts. We studied the links between MRI-derived heart and brain structure and function in the UK Biobank population-based cohort.
Methods Image acquisition and analysis was according to pre-defined protocols. We included the following cardiovascular metrics: left ventricular (LV) stroke volume (LVSV), LV global functional index (LVGFI), LV mass to LV end-diastolic volume ratio (LVM: LVEDV), global longitudinal strain (GLS), left atrial ejection fraction (LAEF), aortic distensibility (AoD). T1 and T2 structural images were used to determine overall brain volume, volume of white matter hyperintensities, and volumes of several subcortical structures. We considered microscopic features of white matter integrity assessed using diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI), across a range of white matter fibre tracts. Associations between heart and brain measures were computed using standardised betas from multivariable linear regression models, adjusted for age, sex, deprivation, obesity, education level, alcohol consumption, diabetes, hypertension, high cholesterol, smoking, physical activity, systolic blood pressure, total cholesterol, and glycosylated haemoglobin.
Results We studied 30,373 participants; average age was 63±7.5 years-old; 52% were women. Adverse cardiovascular phenotypes across all metrics were associated with larger volume of white matter hyperintensities (e.g., LV GFI: Beta=−0.049; 95% CI=[−0.060, −0.039]; p-value= 3.82×10−20). Higher LVSV (Beta= 0.031; 95% CI= [0.022, 0.039]; p-value= 1.57×10−12) and greater AoD (Beta=0.027; 95% CI= [0.016, 0.039]; p-value= 5.76×10−6) were associated with larger total grey matter volumes. Higher LV GFI, higher LAEF, and higher AoD were associated with healthier white matter microstructure as per higher neurite density and stronger myelin membranes (e.g., fractional anisotropy with LV GFI: Beta= 0.052; 95% CI= [0.040, 0.064]; p-value= 1.79×10−17). Healthy white matter microstructure was associated with less concentric LV hypertrophy (LVM: LVEDV: Beta= −0.051; 95% CI= [−0.064, −0.038]; p-value= 2.94×10−15) and better GLS (Beta= −0.032; 95% CI= [−0.044, −0.019]; p-value= 4.89×10−7).
Conclusion In this large population cohort, we demonstrate independent links between heart and brain health using detailed MRI. Participants with healthier hearts had significantly less brain atrophy, less brain microvascular injury, and healthier neuronal structure.
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