High blood pressure and large increases in blood pressure in midlife (age 36 to 53 years) may be associated with brain pathologies in later life, according to a study published online in The Lancet Neurology on August 20, 2019.

The participants numbering 502 were from Insight 46, a neuroscience sub-study of the Medical Research Council (MRC) National Survey of Health and Development, one of the oldest British birth cohort studies, that has followed 5362 individuals since their birth in England, Scotland and Wales during one week in March 1946.

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Specialists know that high blood pressure increases the risk for cognitive impairment later in life, but they do not know exactly how and when it increases the risk. The new study tracked blood pressure of a group of people aged 36 to 69 years to explore its influence on the brain, and found that the link may be there from a younger age than anticipated.

In a press release, Professor Jonathan M Schott, University College London, UK, the lead author, stated that their research builds on existing evidence around the role of blood pressure and subsequent brain pathology. They 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.

"We speculate that these changes may, over time, result in a decline in brain function for example impairments in thinking and behaviour, so making the case for targeting blood pressure in mid-life, if not earlier", he cautioned.

The participants in the study were cognitively healthy at the age of 70. Scientists have measured their the blood pressure at age 36, 43, 53, 60 to 64, and 69 years and also calculated the blood pressure changes between the readings.

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“Our study design provides a unique opportunity to examine blood pressure at different ages, blood pressure changes during specific periods from early adulthood to late life, and to explore their influences on brain pathologies and brain volumes. As increases 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.”, co-author, Dr. Josephine Barnes, University College London, UK, clarified in the press release.

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Limitations

The researchers admit that the study has some limitations. The results may be less generalisable to people in other age groups; as with any birth cohort, participants have gone through life phases at the same time, and will have been exposed to the same treatments and targets for blood pressure, which may differ from people of different ages.

The Insight 46 cohort is exclusively white British people, and in addition, slightly under-represents people with poor overall health, which reduces how these findings, can be applied to different populations. The individuals included in the analyses were cognitively normal, and, as only few individuals in their early 70s have cognitive decline, the authors believe that the cognitive effects of the brain changes they observed may be seen later in life.

Finally, there are other brain pathologies, which can lead to dementia, which further research should explore.

"Our study presents the first work, to our knowledge, examining the association between blood pressure taken prospectively at multiple time-points, blood pressure changes, and brain pathologies and volumes measured systematically in a birth cohort in which all participants are of a near-identical age." the researchers claimed

"The study design provides a unique opportunity to examine blood pressure changes in well-defined periods from early adulthood into midlife to late life and to explore their effect on brain pathologies and brain volumes.", they added

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In a linked Comment, Dr. Lenore J Launer of the National Institute on Ageing, NIH, Bethesda, USA, asserted that although there are several major translational efforts to more completely understand the complexity of blood pressure–cognitive-related outcomes, the simple association between blood pressure and cognitive-related brain pathology is unlikely to be a chance finding.

"Millions of individuals have unhealthy blood pressure. Immediate attention should be given to efforts to control blood pressure through clinical services and public health interventions and to alleviate the barriers to delivery and uptake of these messages.” he noted

“The study itself is very high-quality research, with solid data and sound conclusions. It is an excellent addition to existing literature, contributing to understanding the link between cerebrovascular health in middle age and healthy ageing of the brain." Dr. Karen Doyle, Senior Lecturer in Physiology, National University of Ireland Galway, stated in a release from Science Media Centre.

“It clearly implicates high blood pressure as a cause of white matter lesions and smaller brain volume later in life. It also distinguishes between the effects of high blood pressure on two known causes of dementia – small cerebral blood vessel disease is increased with high blood pressure, but there is no significant link to the amyloid pathology of Alzheimer’s disease.

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Nevertheless, the overall conclusion that earlier monitoring and intervention to reduce high blood pressure will help to protect the brain as we age, is sound.”, she concluded.

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In the press release published by the Science Media Centre Dr. James Pickett, Head of Research, Alzheimer’s Society, concluded:

“The management of blood pressure is emerging as one of the more robust and modifiable risk factors for dementia, particularly in mid-life. The major strength of this study is that it used a series of measures across a period of around 33 years, giving researchers an impression of how changes in the person’s blood pressure can reflect changes in the brain or risk of dementia."

“We know what’s good for the heart is good for the brain, this research shows that it is never too early to start thinking about you can do to maintain healthy blood pressure – from eating a balanced diet to avoiding smoking and excessive drinking. Another good place to start the conversation for people over the age of 40 is with an NHS Health Check with a health professional every five years.”

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Prof. Paul Leeson, Professor of Cardiovascular Medicine, University of Oxford, said:

“A unique strength of this new study is that the people involved have been taking part in the research for many decades. This has allowed the authors to study how variations in blood pressure when they were young associate with brain structure when the participants reached their 70s.

“The group taking part is relatively small so it is difficult to make strong conclusions, and this new paper is not a trial, so we still do not know whether treating the high blood pressure when the participants were younger could have prevented these differences in the brain. However, the findings do support the idea that there may be critical periods in life, such as in your 30s and 40s, when periods of high blood pressure are accelerating damage within the brain.”

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Prof. Tara Spires-Jones, UK Dementia Research Institute Programme Lead and Deputy Director, Centre for Discovery Brain Sciences, University of Edinburgh, another expert from the Science Media Centre said:

“Based on these data, authors suggest it may be beneficial to begin monitoring blood pressure in people in their 30s and to begin treating people with high blood pressure early to maximize brain health in older age."

Everyone including the specialists assert that those with high BP must treat it promptly regardless of their age to protect their heart and brain.

The author, Dr. K S Parthasarathy is a freelance science journalist and a former Secretary of the Atomic Energy Regulatory Board. He is available at ksparth@yahoo.co.uk