Post by Deborah Joye
What's the science?
High blood pressure, also known as hypertension, is a common health issue in adults that tends to get worse with age. Hypertension in midlife (between 40 and 70 years of age) is also associated with increased risk for brain pathology later in life, including cerebrovascular disease (disorders that affect blood supply to the brain) and Alzheimer’s disease. But how might changes in blood pressure result in late-life brain pathology, and at what age are people most sensitive to these changes? This week in The Lancet Neurology, Lane and colleagues study longitudinal blood pressure changes and late-life brain scans, revealing that increases in blood pressure from early adulthood into midlife are associated with increased white matter hyperintensity volume and smaller brain volumes in late-life (around age 70).
How did they do it?
The authors analyzed data from Insight 46, a neuroscience substudy of over 5000 individuals born throughout mainland Britain during one week in 1946. Over the course of the study, blood pressure measurements were collected at ages 36, 43, 53, 60-64, and 69 years. From 2015 through 2018, the authors recruited close to 500 participants of Insight 46 (mean age 70.7 years) to undergo brain-imaging MRI scans and determine possible neurological changes. The primary measures were white matter hyperintensity volume, a marker of vascular disease in the brain; presence of amyloid-beta, a hallmark pathology in Alzheimer’s disease; whole-brain and hippocampal volumes, to determine possible reductions in brain size; and tests of episodic memory, processing speed, and global cognition using the Preclinical Alzheimer Cognitive Composite.
What did they find?
The authors found that increased systolic and diastolic blood pressure were associated with greater white matter hyperintensity volume at all measured ages, with a stronger association after 53 years of age. Higher systolic blood pressure across time points was associated with smaller whole-brain volume, and greater increases in systolic blood pressure between 36 and 43 years old were associated with smaller hippocampal volume. Interestingly, blood pressure at any age was not associated with the presence of amyloid-beta, and there were no consistent associations between blood pressure and scores on cognitive tests.
What's the impact?
This study is the first to examine blood pressure at multiple timepoints and associate blood pressure changes with systematically measured brain pathologies and volumes. The authors show that early adulthood into midlife may present a sensitive period where rapid increases in blood pressure can affect brain pathologies such as white matter hyperintensities in later life. It should be noted that the participants of this study were exclusively white British participants broadly representative of the population of mainland Britain born in 1946; however, this may reduce generalizability to other ageing populations. These findings suggest that blood pressure management may need to begin at or before age 40 to prevent negative impacts on late-life brain health.
Lane et al., Associations between blood pressure across adulthood and late-life brain structure and pathology in the neuroscience substudy of the 1946 British birth cohort (Insight 46): an epidemiological study, The Lancet Neurology (2019). Access the original scientific publication here.