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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 4, July/August 2021
192
AFRICA
Above-normal blood pressure in midlife linked to increased brain damage in later life
Higher-than-normal blood pressure, especially diastolic, is
linked to more extensive brain damage in later life, according
to a study in the
European Heart Journal
. In particular, the
study found that there was a strong association between
diastolic blood pressure before the age of 50 years and brain
damage in later life, even if the diastolic blood pressure was
within what is normally considered to be a healthy range.
The findings come from a study of 37 041 participants
enrolled in UK Biobank, a large group of people recruited
from the general population aged between 40 and 69 years,
and for whom medical information, including MRI brain
scans was available.
The research, carried out by Dr Karolina Wartolowska,
a clinical research fellow at the Centre for Prevention of
Stroke and Dementia, University of Oxford, UK, looked
for damage in the brain called ‘white matter hyperintensities’
(WMH). These show up on MRI brain scans as brighter
regions and they indicate damage to the small blood vessels
in the brain that increases with age and blood pressure.
WMH are associated with an increased risk of stroke,
dementia, physical disabilities, depression and a decline in
thinking abilities.
Dr Wartolowska said: ‘Not all people develop these
changes as they age, but they are present in more than 50%
of patients over the age of 65 years and most people over the
age of 80 years even without high blood pressure, but it is
more likely to develop with higher blood pressure and more
likely to become severe.’
Information on the participants was collected when
they enrolled in UK Biobank between March 2006 and
October 2010, and follow-up data, including MRI scans,
were acquired between August 2014 and October 2019.
The researchers adjusted the information to take account
of factors such as age, gender, risk factors such as smoking
and diabetes, and diastolic as well as systolic blood pressure.
Systolic blood pressure is the maximum blood pressure
reached each time the heart beats and is the top number in
blood pressure measurements.
‘To compare the volume of white matter WMH between
people and to adjust the analysis for the fact that people’s
brains vary slightly in size, we divided the volume of WMH
by the total volume of white matter in the brain. In that way,
we could analyse the WMH load, which is the proportion of
the WMH volume to the total volume of white matter,’ said
Dr Wartolowska.
The researchers found that a higher load of WMH was
strongly associated with current systolic blood pressure,
but the strongest association was for past diastolic blood
pressure, particularly when under the age of 50 years. Any
increase in blood pressure, even below the usual treatment
threshold of 140 mmHg for systolic and below 90 mmHg
for diastolic, was linked to increased WMH, especially when
people were taking medication to treat high blood pressure.
For every 10-mmHg increase in systolic blood pressure
above the normal range, the proportion of WMH load
increased by an average (median) of 1.126-fold and by 1.106-
fold for every 5-mmHg increase in diastolic blood pressure.
Among the top 10% of people with the greatest WMH load,
24% of the load could be attributed to having a systolic
blood pressure above 120 mmHg, and 7% could be attributed
to having diastolic blood pressure above 70 mmHg, which
reflects the fact that there is a greater incidence of elevated
systolic rather than diastolic blood pressure in older patients.
Dr Wartolowska said: ‘We made two important findings.
Firstly, the study showed that diastolic blood pressure in
people in their 40s and 50s is associated with more extensive
brain damage years later. This means that it is not just the
systolic blood pressure, the first, higher number, but the
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