Measuring blood pressure is a common occurrence in doctors’ offices. Blood pressure that is too high (hypertension) can increase the risk of serious health conditions, and pressure that is too low (hypotension) can cause light-headedness and fainting. Previous studies have shown that blood pressure readings can vary depending on where on the body the measurement is taken from, and can even be different in each arm. However, new findings published in the journal Hypertension suggest that this variance could have major implications.
The study was conducted by the Inter-arm Blood Pressure Difference - Individual Participant Data (INTERPRESS-IPD) Collaboration and led by the University of Exeter. They analyzed data from 24 studies where blood pressure in both arms was measured. The studies were conducted internationally, with 14 from Western Europe, 7 from the US, 2 from East Asia, and 1 from Sub-Saharan Africa. Data was collected from 53,827 participants whose deaths, heart attacks, and strokes were tracked over 10 years.
Blood pressure measurements are given as systolic and diastolic – the maximum and minimum measurements respectively – in millimeters of mercury (mmHg). Having systolic pressure below 140 mmHg and diastolic pressure below 90 mmHg is considered healthy.
The results of the study showed that having too great of a difference in systolic blood pressure between arms could signify health risks. In fact, people with a difference of just 5 mmHg had higher mortality rates. On top of this, each mmHg difference increased risk of heart attacks, strokes, and new angina by 1%. "We've long known that a difference in blood pressure between the two arms is linked to poorer health outcomes. The large numbers involved in the INTERPRESS-IPD study help us to understand this in more detail. It tells us that the higher the difference in blood pressure between arms, the greater the cardiovascular risk” said lead author Dr Chris Clark in a statement.
Currently, a pressure difference of 15 mmHg between the arms is the threshold to identify patients at risk of complications, but this study indicates that the threshold should be lowered. "We believe that a 10 mmHg difference can now reasonably be regarded as an upper limit of normal for systolic inter-arm blood pressure, when both arms are measured in sequence during routine clinical appointments. This information should be incorporated into future guidelines and clinical practice in assessing cardiovascular risk. It would mean many more people were considered for treatment that could reduce their risk of heart attack, stroke and death." Says co-author Professor Victor Aboyans, head of the Department of Cardiology at Dupuytren University Hospital in France.
Measuring blood pressure in both arms is advised, but this advice is often ignored. Dr Clark elaborates, “Whilst international guidelines currently recommend that this is done, it only happens around half of the time at best, usually due to time constraints. Our research shows that the little extra time it takes to measure both arms could ultimately save lives".