Blood pressure is a vital sign, as too high or too low blood pressure is an indication that something is wrong with your health, which could lead to serious conditions such as stroke and heart disease. Accurate and regular blood pressure readings are a quick and easy way to catch any heart issues early. How and when to take blood pressure readings are important, as the way you prepare for the test and even the position of your arm can change the reading by 10% or more. Of concern is the phenomenon that some people’s blood pressure rises dangerously high at night, but reflect normally during the day when readings are usually taken, which may lead to unexpected cardiovascular events such as heart attack.
Importance of checking blood pressure at home:
Organizations such as the American Heart Association recommend that people with elevated blood pressure regularly monitor their blood pressure at home. By self-monitoring, high blood pressure (hypertension) can be diagnosed earlier than by only having occasional blood pressure readings taken at a medical practitioner. Self-monitoring is also a measure of the effectiveness of blood pressure medication, and may also serve to motivate the individual to control blood pressure with improved diet and physical activity.
Nervousness during a medical visit can cause spikes in blood pressure and this phenomenon is such a common occurrence, it is called white coat hypertension! By regularly keeping track of blood pressure at home, it can help determine if you really have high blood pressure.
When to measure blood pressure:
Initially measure blood pressure at least twice daily, first in the morning and again in the evening, to establish a pattern. Empty your bladder first, as a full bladder slightly increases blood pressure, and before eating, exercising, or taking any medication in the morning. Also avoid alcohol, caffeine, tobacco and food for 30 minutes before taking a reading.
However, in spite of regular blood pressure monitoring and readings within the normal range for the individual’s age group, some people are unbeknown candidates for heart attack or stroke. A 2022 study by the University of Oxford found that about 15% of people in the age group 40-75 may have a form of undiagnosed high blood pressure that occurs only at night-time while asleep. As they are unaware of this condition, they are at a higher risk of cardiovascular disease such as heart failure, stroke, and even death. As home blood pressure monitors cannot be used when the individual is asleep, night-time blood pressure is not measured.
The study looked at 24-hour blood pressure patterns in patients admitted to hospital, as well as patients in primary care in the community, and found that individuals can be divided into three groups according to their blood pressure pattern:
- Dippers – whose night-time blood pressure is lower than the day-time blood pressure, which is the normal pattern for healthy young people.
- Non-dippers – whose night-time and day-time blood pressure readings are not much different.
- Reverse dippers – whose night-time blood pressure is higher than day-time blood pressure. This is more prevalent amongst older people.
Evidence from research shows that reverse dippers are at higher risk for cardiovascular disease and that at least 1 in 3 reverse dippers had at least one cardiovascular disease.
The Oxford research team suggests that patients being assessed for hypertension by their medical practitioners should be offered 24-hour ambulatory blood pressure monitoring (APBM) at home for all patients 60 years or older. Night-time blood pressure increases with age and normal self-monitoring at home would not pick up high night-time blood pressure.
How to self-monitor blood pressure:
What you do beforehand can influence blood pressure readings, which may be high due to stress, recent exercise, a full stomach or full bladder, drinking a caffeinated beverage or smoking during the 30 minutes before the test, or certain medications such as anti-inflammatories and decongestants.
Some tips to properly take blood pressure from Harvard Medical School:
- Sit quietly for about five minutes before measuring.
- The inflatable part of the cuff should cover at least 80% of your upper arm.
- The cuff should be placed on bare skin and not over clothes.
- Refrain from talking during the measurement.
- Measure your blood pressure twice, with a brief break in between. Should the readings differ by 5 points or more, take a third reading.
- The best position is seated in a chair with your feet uncrossed on the floor and your arm supported to allow your elbow to be at heart level. Remain in the same position throughout the measurement.
With regard to the last item, preliminary research findings from a large, long-running study have found that lying down for blood pressure readings might reveal more than expected about heart health. When compared with readings taken when someone was sitting down, readings showing high blood pressure in people who were lying down can better predict stroke and serious heart problems, and even death.
These findings suggest that having people lying flat to measure blood pressure could potentially help to identify people who need treatment, despite normal looking readings taken while seated.
The study used data from 11 369 participants without a history of heart disease, heart failure, or stroke and they had been followed for 25 to 28 years. Their blood pressure was measured both while seated and while lying down. They were divided into four groups:
- One group had normal blood pressure readings both when seated and lying down.
- One group had high blood pressure only while seated.
- The third group, about 16% of participants, had high blood pressure only while lying down.
- The fourth group had high blood pressure in both positions.
Over time, the third group with high blood pressure only while lying down had similar risk levels for cardiovascular disease than the fourth group with high blood pressure in both positions. These higher risks included coronary heart disease (53%), heart failure (51%), stroke (62%), fatal coronary heart disease (78%), and a 34% higher risk of death from all causes, compared to participants with normal blood pressure in both positions.
The findings imply that checking blood pressure while lying down might unveil high blood pressure that would otherwise be missed during a routine measurement while seated in the doctor’s office.
Understanding blood pressure readings:
Blood pressure readings for adults are categorized as follows:
- Normal blood pressure: Less than 120/80 mm Hg.
- Elevated blood pressure: 120/80 to 129/79 mm Hg.
- Stage 1 hypertension: 130/80 to 139/89 mm Hg.
- Stage 2 hypertension: 140/90 mm Hg and above.
Conclusion:
Over time, uncontrolled high blood pressure can lead to complications not only in terms of cardiovascular related diseases such as strokes and heart disease, but also to chronic kidney disease and eye problems.
Recording regular blood pressure readings at home, such as the date time of day, systolic and diastolic numbers, and heart rate will help you to notice any patterns or shifts in the results. It might be a good idea to take blood pressure readings both when seated and when lying down, just to cover all bases when there are shifts from your normal range of blood pressure readings.
If the systolic pressure (the blood force against the artery walls as the heart beats) rises to 130 or more, and the diastolic pressure (blood pressure between heartbeats) rises to 80 or more, it is time to talk to your doctor. When assessing hypertension, your doctor should suggest 24-hour ambulatory blood pressure monitoring (APBM) at home, which would also determine during night-time whether you are a dipper, a non-dipper, or a reverse-dipper.
You may be able to lower highish blood pressure through some simple lifestyle changes such as increasing exercise, reducing salt and alcohol, quitting smoking, and eating a well-balanced diet. Your life may depend on it.
References:
Why you should take your blood pressure at home, and how to do it. Published 27 December 2021. Cleveland Clinic. USA. (A nonprofit multi-specialty medical centre that integrates clinical and hospital care with research and education.) (www.clevelandclinic.org)
Get the most out of home blood pressure monitoring. Published 23 July 2024. Mayo Clinic. USA. (www.mayoclinic.org)
Tips to measure your blood pressure correctly. Published 24 September 2024. Harvard Health Publishing. Harvard Medical School. (www.health.harvard.edu)
Night-time blood pressure assessment is found to be important in diagnosing hypertension. Published 23 September 2022. University of Oxford. UK. (www.ox.ac.uk)
Diagnosing hypertension in primary care: a retrospective cohort study to investigate the importance of night-time blood pressure assessment. Published in the British Journal of General Practice. 2023; 73 (726). (www.bjgp.org)
A surprising finding about taking blood pressure lying down. Published 8 September 2023. American Heart Association. (www.heart.org)
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