HYPERTENSION or high blood pressure, remains a major risk factor for cardiovascular disease and stroke, affecting 48 per cent of adults in the United States.

According to the Jamaica Health and Lifestyle Survey for 2016/17, about 1 in 3 adult Jamaicans have hypertension, with more prevalence in women (35.8 per cent) than men (31.7 per cent). The survey further highlighted that 60 per cent of men and 26 per cent of women were unaware of their blood pressure status. The Centers for Disease Control and Prevention, USA, in 2021 reported that hypertension was a major cause of nearly 700,000 deaths in the US.

In today’s column we will discuss blood pressure monitoring at home. How should this be done? How often? And what do the numbers mean?

Managing high blood pressure, or hypertension, has long been recognised as an essential component of heart health care. According to older research, blood pressure may be higher while lying down, but more recent studies have contradicted this finding and suggest that blood pressure may be lower while lying down versus sitting.

As defined by the American Heart Association (AHA) and American College of Cardiology, normal blood pressure for adults measured in a seated position is a systolic reading of less than 120 mmHg and a diastolic reading under 80 mmHg. Readings fluctuate throughout the day, though.

The “gold standard” for accuracy of blood pressure measurement is ambulatory blood pressure monitoring, which takes readings throughout the day. But that requires wearing a monitor for 24 hours.

Over the years, research has shown repeatedly that night-time blood pressure measurements are one of the best predictors of cardiovascular disease. But it’s hard to get such readings. Currently, the American Heart Association recommends that blood pressure readings be taken when you’re sitting down. But getting an accurate reading from a seated position can be complicated, and several investigators now question whether a sitting position is indeed the best way to check blood pressure in healthy patients.

How should blood pressure be measured, and what is the evidence?

Traditional teaching states that blood pressure is best measured in the sitting position with a recommendation to sit with your back straight and supported and feet flat on the floor with the legs uncrossed. Your arm should be supported on a flat surface, such as a table, with the upper arm at heart level. This classical approach has recently been challenged by some scientific data suggesting that lying flat or standing may be as appropriate or even more accurate and more desirable. In a recent study, scientists at UT Southwestern (UTSW) have suggested that measuring blood pressure while standing rather than sitting provided a more accurate or reliable reading and could lead to significant improvements in early detection of high blood pressure in healthy adults.

UTSW researchers measured the blood pressure of 125 healthy patients ages 18-80 with no history of hypertension, previous use of blood pressure medication, or other comorbidities, and used statistical methods to assess the overall accuracy of each test in diagnosing hypertension. Their findings revealed that measuring standing blood pressure either on its own or in addition to sitting blood pressure significantly improved diagnostic accuracy.

In all patients studied, blood pressure was determined through 24-hour ambulatory blood pressure monitoring (ABPM), seated in the doctor’s office, and standing in the office. Using 24-hour ambulatory pressure measurement as the gold standard the accuracy in detecting high blood pressure and the accuracy in detecting absence of hypertension in the seated measurements were 43 per cent and 92 per cent, while in the standing measurements accuracy of detection or absence were 71 per cent and 67 per cent.

In another recent study, investigators sought to determine whether simply having people lie down in the clinic during the day might identify those at higher risk of cardiovascular disease, similar to blood pressure measurements taken during sleep.

Using data from a large, longitudinal study, researchers found that when compared with readings taken while sitting, readings that showed high blood pressure in people who were lying down did a much better job of predicting stroke, serious heart problems and death.

These findings were surprising and suggest that having people lie flat to measure their blood pressure could potentially help identify people who need treatment, despite seemingly normal readings taken while seated.

The findings imply that checking supine blood pressure might unveil hypertension that would otherwise be missed in the doctor’s office.

Whether sitting, lying down, or standing, what is important is to make sure that you are still, in a noise-free zone, and that the bottom of the cuff is placed directly above the bend of the elbow. Follow your monitor’s instructions for an illustration or have your health-care professional show you how.

It is preferable that you do not smoke, drink caffeinated beverages, or exercise within 30 minutes before measuring your blood pressure. Empty your bladder and ensure at least five minutes of quiet rest before measurements. For more reliable assessment of variations in blood pressure readings, it is recommended that readings are performed at the same time each day – for example, mornings and evenings. Multiple readings over a period of two weeks are ideal for a more informed assessment of blood pressure status.

Dr Ernest Madu, MD, FACC and Dr Paul Edwards, MD, FACC are consultant cardiologists for the Heart Institute of the Caribbean (HIC) and HIC Heart Hospital. HIC is the regional centre of excellence for cardiovascular care in the English-speaking Caribbean and has pioneered a transformation in the way cardiovascular care is delivered in the region. HIC Heart Hospital is registered by the Ministry of Health and Wellness and is the only heart hospital in Jamaica. Send correspondence to info@caribbeanheart.com or call 876-906-2107.