Is Blood Pressure Higher At Night?

High blood pressure, also known as hypertension, is a major risk factor for heart disease and stroke. It is a cause of chronic kidney disease, too. Affecting over 12 million people in the United Kingdom, hypertension is the single most important preventable cause of premature death.

While it is possible to improve blood pressure control by dietary and lifestyle changes, medication is often needed for patients for whom lifestyle changes are insufficient or ineffective. Meanwhile, regular blood pressure monitoring is also paramount for effective blood pressure control.

Nighttime blood pressure has been thought to be a strong predictor of both heart disease and stroke and previous studies had indicated that blood pressure measured over the arm falls at night during sleep.

However, the new data collected by researchers from University College London (UCL) using the new technology showed that the nighttime decline in blood pressure might be less extensive than previously thought. The findings were published in the June 2013’s issue of the journal ‘Hypertension’.

With the support by the National Institute for Health Research (NIHR), they developed a portable wrist watch-based device together with a Singaporean technology company (Healthstats International). The device contains a sensor in the strap that detects the pulse wave at the wrist, rather than measuring the pressure directly. By mathematically modeling the pulse wave, pressure at the aortic root (close to the heart) could be measured accurately over a full 24-hour period, without disturbing the person being monitored.

Patterns of brachial blood pressures (in the arm) and central aortic pressures (where blood exits the heart) were measured at the same time. Though similarities in the circadian rhythms of brachial and central aortic pressures were found, there was a significantly reduced nighttime dip in central aortic pressure relative to the corresponding nighttime dip in brachial pressure. The pressures by the heart do not dip as much during sleep as previously thought based on conventional pressure measurements taken from the arm.

The findings suggested that nocturnal aortic pressures are disproportionately higher than brachial pressures during sleep. Such information is very useful for professionals who are investigating the damage in the brain and heart caused by high blood pressure, and can have significant implications for the evaluation of future therapies. This would probably change the way high blood pressure is measured and treated.

Since the new developed watch can be worn continuously, it is possible for the health experts to program the device to sample the pulse wave day and night, and obtain measurements of the aortic pressure over a 24-hour period.