High blood pressure in young people could lead to poor brain health in later years
Changes in blood pressure in those as young as 36 have now been linked with poor brain health. The ages of 36-53 appear to be a "sensitive period" when high blood pressure and increase in blood pressure might be particularly damaging to the brain, according to an observational study of 502 people who have been tracked since their birth in 1946.
Researchers found that high blood pressure and rising blood pressure between ages 36-53 (from early adulthood into midlife) are associated with smaller brain volume and white matter lesions in later years, at 69-71 years of age.
The study, funded by Alzheimer's Research UK, MRC Dementias Platform UK, Wellcome, Brain Research UK, the Wolfson Foundation and the Weston Brain Institute, allows for a unique perspective on the risk factors throughout life that impact brain health at the age of 70.
High blood pressure is known to increase the risk of cognitive impairment later in life, but exactly how and when it increases risk is unclear. The new study tracked blood pressure from ages 36-69 to explore its influence on the brain and found that the link may be there from a younger age than anticipated.
“The study suggests that the fourth to sixth decades of life could be a sensitive phase when higher blood pressure and increases in blood pressure have a particular impact on the future health of the brain," says the team.
Accordingly, the researchers recommend that blood pressure monitoring and interventions need to start at, or before, 40 years to maximize later brain health. Besides, they add, different approaches to blood pressure change may be needed at different ages.
"Our research builds on existing evidence around the role of blood pressure and subsequent brain pathology. We found that higher and rising blood pressure between the ages of 36 and 53 had the strongest associations with smaller brain volume and increases in white matter brain lesions in later life,” says lead author Professor Jonathan M Schott from the University College London, UK.
He adds, "We speculate that these changes may, over time, result in a decline in brain function, for example, impairments in thinking and behavior, so making the case for targeting blood pressure in mid-life, if not earlier."
Co-author, Dr. Josephine Barnes, University College London, UK, says: "Increase in blood pressure and higher blood pressure between the ages of 36 and 53 seem to have a detrimental effect on brain health in later life. These findings reinforce the need for monitoring blood pressure even before mid-life."
There was, however, no evidence that blood pressure affected cognition or the build-up of beta-amyloid plaques. This suggests that associations between midlife blood pressure and late-life brain health are unlikely to be occurring through the build-up of beta-amyloid, which is thought to be one of the earliest changes seen in Alzheimer’s disease.
"The findings suggest that high blood pressure (140/90 mm Hg or higher) may lead to reductions in brain volume and higher levels of white matter hyper-intensities within the brain (white matter brain lesions), but not with reduced cognition or the build-up of beta-amyloid plaques — one of the key proteins associated with Alzheimer’s disease," says the study.
The findings from the "Insight 46" study have been published in The Lancet Neurology. Insight 46 is a neuroscience sub-study of the MRC National Survey of Health and Development (NSHD), the longest-running birth cohort in the UK.
Insight 46 is designed to follow over 500 birth cohort members to look for early signs and risk factors for dementia as they reach their 70s. Dementia affects 44 million people worldwide, a number predicted to triple by 2050.
Up to a third of dementia risk might be modifiable. Hypertension, particularly in midlife, is associated with late-life dementia risk and with risk of clinically diagnosed Alzheimer’s disease.
According to researchers, while blood pressure in midlife has previously been linked to a higher risk of dementia, but the mechanism by which this happens, and the time when blood pressure is most important, remain to be fully understood.
To answer these questions, the research team followed 502 individuals, who were all born in Britain in the same week in 1946. The participants were free from dementia at the start of the study, and 465 underwent brain scans to assess their brain health.
All participants had blood pressure taken at 36, 43, 53, 60-64, and 69 years of age, and blood pressure changes between the readings were calculated.
The brain scans looked for levels of an essential Alzheimer's protein, amyloid, in the brain. The scans also assessed the size of the brain — an indicator of brain health — and the presence of blood vessel damage in the brain.
The results show that higher blood pressure at the age of 53 and faster rises in blood pressure between 43 and 53 was associated with more signs of blood vessel damage or "mini-strokes" in the brain when an individual was in their early 70s.
Higher blood pressure at the age of 43 and greater increases in blood pressure between the ages of 36 and 43 was associated with smaller brain volumes. Blood pressure was not associated with the amount of amyloid protein in the brain and did not appear to predict memory and thinking problems at this age.
"Having higher blood pressure at age 53 and greater increases in blood pressure between 43 and 53 were associated with having more white matter lesions at 70 (for example, having 10mmHg higher systolic or diastolic blood pressure when aged between 43 and 53 was associated with about 7% and 15% more white matter lesions, respectively).
Higher blood pressure aged 43 and greater increases in blood pressure from the age of 36 were associated with having smaller brain volumes (for example, having a 10mmHg higher diastolic blood pressure aged 43 was associated with having a 6.9mL smaller brain at about age 70)," the findings state.
According to Professor Jonathan Schott from UCL Queen Square Institute of Neurology, this unique group of individuals, who have contributed to research their entire lives, has already shaped scientists’ understanding of the factors influencing health throughout life.
“The Insight 46 study has allowed us to reveal more about the complex relationship between blood pressure and brain health. The findings suggest that blood pressure, even in our 30s, could have a knock-on effect on brain health four decades later. We now know that damage caused by high blood pressure is unlikely to be driven through the hallmark Alzheimer’s protein amyloid but through changes in blood vessels and the brain’s architecture,” says Schott.
The Insight 46 study will continue to monitor these participants in the years to come to understand whether those with worse brain health are more prone to cognitive decline and dementia.
"Although this study must continue to assess the impact of blood pressure on dementia risk, the findings shed new light on the mechanism by which hypertension could damage the brain," says Dr. Carol Routledge, Director of Research at Alzheimer’s Research, UK. She says, "As the participants in this study are identical ages and have been followed throughout life, the researchers can gain robust insights into the factors influencing their brain health"
She adds, "High blood pressure in midlife is one of the strongest lifestyle risk factors for dementia, and one that is in our control to easily monitor and manage. Research is already suggesting that more aggressive treatment of high blood pressure in recent years could be improving the brain health of today’s older generations. We must continue to build on this insight by detecting and managing high blood pressure even for those in early midlife."