Blood Pressure and Progression of Brain Atrophy: The SMART-MR Study
What is the association of baseline blood pressure (BP) and change in BP over time with progression of brain atrophy?
The SMART-MR (Secondary Manifestations of ARTerial disease–Magnetic Resonance) study was a prospective cohort study at the University Medical Center Utrecht, the Netherlands, with baseline measurements in 2001-2005, and follow-up measurements in 2006-2009. The mean follow-up time was 3.9 years. A total of 663 patients (mean [standard deviation] age, 57  years; 81% male) with coronary artery disease, cerebrovascular disease, peripheral artery disease, or abdominal aortic aneurysm were included. Using automated segmentation at baseline and follow-up, change in brain parenchymal fraction, cortical gray matter fraction, and ventricular fraction (%ICV) were quantified as indicators of progression of global, cortical, and subcortical brain atrophy.
Multivariable adjusted regression analysis showed that patients with lower baseline diastolic BP (DBP) or mean arterial pressure (MAP) had more progression of subcortical atrophy. The mean differences in the change in ventricular fraction between low and high DBP was 0.07% (95% confidence interval [CI], 0.01-0.14) and between low and high MAP was 0.05% (95% CI, 0.00-0.10). Furthermore, in patients with higher baseline BP (DBP, MAP, or systolic BP [SBP]), those with declining BP levels over time had less progression of subcortical atrophy compared with those with rising BP levels.
The authors concluded that in patients with manifest arterial disease, low baseline DBP was associated with more progression of subcortical atrophy, irrespective of the BP course during follow-up.
This prospective study in patients with manifest arterial disease suggests that low DBP (and MAP) at baseline were associated with more progression of subcortical atrophy, irrespective of the course of the BP levels during follow-up, and declining DBP, MAP, and, to a lesser extent, SBP levels over time in patients with higher baseline BP were associated with less progression of subcortical brain atrophy. Overall, the data appear to imply that BP lowering is beneficial in patients with higher BP levels, but one should be cautious with further BP lowering in patients who already have low BP. The optimal DBP and MAP levels to minimize brain atrophy in patients with existing arterial disease need further study.
Keywords: Coronary Artery Disease, Follow-Up Studies, Arterial Pressure, Transcription Factors, Peripheral Arterial Disease, Magnetic Resonance Imaging, Atrophy, Neurodegenerative Diseases, Cerebrovascular Disorders, Cardiovascular Diseases, Netherlands, Magnetic Resonance Spectroscopy, Aortic Aneurysm, Abdominal, Disease Progression
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