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Associations Between Vascular Risk Factors and Brain MRI Findings
Study Questions:
What are the associations between vascular risk factors and brain health, as measured by magnetic resonance imaging (MRI)?
Methods:
The authors used data from the UK Biobank study that enrolled community dwelling adults. Vascular risk factors identified included the presence of diabetes, hypertension, or hypercholesterolemia; smoking; pulse pressure; waist-hip ratio; and body mass index (BMI). MRI was used to evaluate changes in brain macrostructure and microstructure. All participants underwent imaging on the same scanner using the same protocol. Subjects with a history of brain injury, including stroke or a neurodegenerative disease, were excluded.
Results:
There were 9,772 subjects included. The mean age was 62 years and 53% were women. Male sex and older age were associated with an increased number of vascular risk factors. Older age was associated with global atrophy and negative changes in brain microstructure. In aggregate, a greater number of vascular risk factors was associated with worse brain health. When compared to subjects without vascular risk factors, those with five or six vascular risk factors had lower brain volume, less gray matter, and a greater volume of white matter hyperintensities.
When individual vascular risk factors were assessed, smoking, hypertension, and diabetes were independently associated with poorer brain structure. Higher BMI and waist-hip ratio were associated with worse brain macrostructure findings, but not associated with impairments in microstructure. The contributions of each vascular risk factor were independent and the magnitude that each vascular risk factor influenced brain health was modest. Hypertension had the largest impact, and was associated with worse findings on white matter measures. Hypercholesterolemia was not associated with an independent contribution to MRI findings.
When specific brain regions were analyzed, a greater number of vascular risk factors was associated with lower subcortical volumes. Smoking, hypertension, diabetes, BMI, and waist-hip ratio were associated with decreased temporal lobe volume.
Conclusions:
The authors concluded that vascular risk factors are associated with worse brain health in a dose-response relationship.
Perspective:
While vascular risk factors are associated with the development of stroke and dementia, their individual impact on changes in brain structure have not been well defined. This study showed that vascular risk factors, particularly smoking, hypertension, and diabetes, are associated with worse brain health, as evaluated by MRI. The regional variations in susceptibility to vascular risk factors support the association between these risk factors and Alzheimer disease.
This study suggests that prevention of vascular risk factors should improve brain health. While smoking, which was reported in pack-years, was analyzed continuously, the presence of hypertension and diabetes was analyzed in a binary (yes/no) fashion, so the impact of control of these risk factors on brain health is unclear. By quantifying the effects of specific vascular risk factors, future studies will be able to build on this work.
Clinical Topics: Dyslipidemia, Noninvasive Imaging, Prevention, Homozygous Familial Hypercholesterolemia, Magnetic Resonance Imaging, Hypertension, Smoking, Sleep Apnea
Keywords: Alzheimer Disease, Atrophy, Blood Pressure, Body Mass Index, Brain Injuries, Diabetes Mellitus, Diagnostic Imaging, Hypercholesterolemia, Hypertension, Independent Living, Magnetic Resonance Imaging, Primary Prevention, Risk Factors, Smoking, Stroke, Temporal Lobe, Vascular Diseases, Waist-Hip Ratio
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