While high blood pressure is a major risk factor for cardiovascular disease, the latest research findings also highlight the negative effects of high blood pressure on cognitive function in the brain, as well as the importance of accurate blood pressure measurements.
Higher than normal blood pressure, also known as hypertension, develops if the walls of the larger arteries lose their natural elasticity and become rigid, and smaller blood vessels become narrower. The higher the blood pressure, the higher the risk of health problems. The prevalence of high blood pressure increases with age, affecting an estimated 65% of people 60 years and older. Hypertension is often referred to as a ‘silent killer’ because it usually has no symptoms and as it rarely makes you feel ill, can go undiagnosed until it results in a stroke or a heart problem.
Effects of high blood pressure on cognitive function:
High blood pressure has always been suspected to affect cognitive function, but an extensive study in Brazil has found proof that high blood pressure hastens a decline in thinking skills and memory. The study (by the Medical School and Clinical Hospital, Federal University of Minas Gerais, situated in the city of Belo Horizonte, Brazil) measured items such as memory, verbal fluency, cognitive abilities, and global cognitive score, which was correlated with blood pressure measurements amongst 7063 participants in 2008-2010 and again in 2012-1014.
The findings linked high blood pressure with cognitive decline, affecting both memory and thinking skills. Compared to people with normal blood pressure, those with high blood pressure showed faster declines in cognitive function. The findings also indicated that treatment for high blood pressure seems to reduce or prevent accelerated cognitive decline.
Blood pressure measurement in both arms:
The heart is a pump that keeps blood moving through your arteries to deliver oxygen and nutrients to every tissue and organ in your body. You need a certain amount of pressure in your arteries to keep the blood flowing.
Your blood pressure reading is expressed as two numbers, for example 120/80mmHg, with mmHg standing for millimetres of mercury, which is the unit used for measuring blood pressure. The first number (120) indicates the systolic pressure, and the second number (80) indicates the diastolic pressure. Systolic pressure is the highest level your blood pressure reaches – when the heart contracts and blood is forced through the arteries. Diastolic pressure is the lowest level your blood pressure reaches – when the heart relaxes between each beat.
A study published in February 2021 in the Hypertension journal says that differences in blood pressure readings between the left and right arms (interarm differences) may indicate a higher risk of heart disease. Systolic interarm difference is associated with increased cardiovascular events, cardiovascular mortality, and all-cause mortality. The upper limit for normal systolic interarm difference is 10 mm Hg, and a difference of 5 mm Hg may already indicate a higher risk for cardiovascular events. The higher the interarm difference, the higher the risk. Interarm differences may be the first sign of hardening of the arteries and/or fatty plaque build-up in one of the arms. The study suggests that blood pressure should be measured in both arms during cardiovascular assessment.
The importance of accurate blood pressure measurement, especially amongst older people, was highlighted in a study that investigated the differences between upper-arm cuff and invasive (inside the arteries) blood pressure measurements, with the purpose to identify isolated systolic hypertension (ISH) more accurately. ISH is the most common form of hypertension. Amongst 1695 participants in the study, the prevalence of ISH according to cuff blood pressure measurement was 24%, which figure rose to 38% when measured with the more accurate invasive aortic blood pressure equipment.
Invasive (intra-arterial) blood pressure monitoring involves direct measurement of arterial pressure by inserting a cannula needle, connected to a measuring apparatus, in a suitable artery. This method allows for continuous heartbeat-to heartbeat blood pressure monitoring. This method is commonly used in intensive care units.
Blood pressure numbers:
The blood pressure of adults is generally considered to be high at 140/90mm/Hg or above. The latest guidelines in the USA, published 7 November 2017 in the Journal of the American College of Cardiology, has lowered the threshold to 130/80mmHg and calls this Hypertension Stage 1, while readings of 140/90mmHg is considered as Hypertension Stage 2.
Blood pressure readings higher than 180/120 is regarded as a Hypertensive Crisis and requires immediate medical attention.
Harvard indicates that to obtain accurate blood pressure readings at home, you should sit comfortably with your back supported and your feet flat on the floor. Your arm should be resting on a table with the palm facing up and the elbow at the level of the heart – a pillow can be used if needed to raise the arm.
Association between systolic interarm differences in blood pressure and cardiovascular disease outcomes. Published February 2021. Hypertension. (Journal). (www.ahajournals.org)
Hypertension, prehypertension, and hypertension control. Published February 2021. Hypertension. (Journal). (www.ahajournals.org)
Identifying isolated systolic hypertension from upper-arm cuff blood pressure compared with invasive measures. Published February 2021. Hypertension. (Journal). (www.ahajournals.org)
Control high blood pressure to protect memory and thinking skills. Published March 2021. Harvard Health Letter. Harvard Medical School. (www.health.harvard.edu)
Arm yourself to get better blood pressure readings. Published April 2021. Harvard Men’s Health Watch. Harvard Medical School. (www.health.harvard.edu)
Blood pressure checks: Both sides now? Published April 2021. Harvard Heart Letter. Harvard Medical School. (www.health.harvard.edu)
Which blood pressure number matters most? Published April 2021. Harvard Heart Letter. Harvard Medical School. (www.health.harvard.edu)
Blood pressure and how to lower it naturally, if needed. Published online. Blog. Health Insight. (www.healthinsight.co.za)