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New research sheds light on how to interpret home blood pressure readings
A study looking at home blood pressure readings suggests that a large difference between two readings is useful for predicting future health problems
In a new study based in Japan, 280 men receiving treatment for high blood pressure measured their own blood pressure at home and were followed up for two years to see if they developed health problems. The researchers were aiming to find out what the most useful blood pressure measurements are for predicting heart disease and stroke, so that doctors know who to keep a close eye on.
The men took two systolic blood pressure readings at home within an hour of waking up in the morning. The first and second readings and the average of the two were all found to be equally good at predicting the risk of a heart attack or stroke, and the higher the reading, the higher the risk. The risk of heart attacks and strokes rose by about 4% with every 1 mmHg rise in systolic blood pressure.
Interestingly, the difference between the two readings was important for predicting these health problems. The research, published in the journal, Hypertension Research, found that a large difference between the readings (5mm Hg or more), regardless of whether the blood pressure rose or fell, was linked to a higher risk of heart attacks and strokes.
An average reading of 145 mmHg or more was also linked to a higher risk – even if the difference between readings was small. An average of 125 mmHg or more was also linked to a higher risk for those with a large difference between readings.
The authors concluded that it’s wise for doctors to look at two home blood pressure readings taken on the same occasion and use the average of the two readings, and to pay attention to those with a large difference between the two readings. They found that the risk of serious health problems was highest in those with both a high average reading and a large difference between readings.
Why was this study done?
There has been some focus in recent years on the importance of variation in blood pressure readings for predicting the risk of serious problems including heart disease and stroke. Some guidelines recommend using the average of two home readings (measured on the same occasion) to get an accurate blood pressure reading. Before now, the importance of the first and second reading have been looked at, but not the value of the first, second, and average over time. The second reading is often lower than the first, but it’s not clear whether the difference between the first and second reading is important.
What else do we need to know about the study?
The authors noted that patients with a larger difference between the two readings were more likely to have had a stroke, mini stroke or heart attack in the past, or have other health problems such as diabetes or kidney disease. While the difference between readings could be important in predicting a patients risk, it’s also important to know their history of previous health problems. Patients with a large difference between readings also tended to be older, and the risk of health problems such as stroke is known to increase with age.
The patients included were part of a much larger study called the HONEST trial which includes over 20 000 people. This research looked at the relatively small number of people who had already been in the trial for two years.
Katharine Jenner, CEO of Blood Pressure UK, explains: Home blood pressure monitoring is a great way for many people to keep an eye on their blood pressure and keep track of how well their medications and lifestyle changes are working for them. This study supports what we already know about blood pressure and measuring it – the higher the systolic blood pressure, the higher the risk of health problems later on, and that it’s best to average more than one blood pressure reading to get the best idea of what’s really going on.
This study suggests that it could also be important to look at the difference between blood pressure readings, however, this study was small and it’s still early days. It will be interesting to see if more data is released from the HONEST trial in the coming years to give doctors a clearer understanding of how best to monitor their patients’ blood pressure and identify those most at risk of serious health problems in future.