The importance of monitoring night-time – or nocturnal - blood pressure is being more widely recognised in terms of hypertension management.
Evidence is pointing to nocturnal blood pressure (BP) as increasing the risk of cardiovascular events, such as stroke or coronary heart disease.
But while the value of monitoring nocturnal BP is acknowledged, getting accurate and regular readings at night from individuals without impacting their sleep quality - because of the device cuff inflation and frequency of measurements - is often not straightforward.
Circadian rhythm
The pattern of circadian rhythm of BP can be evaluated by ambulatory blood pressure monitoring, which is a simple recording of blood pressure that requires a person to wear a cuff on the arm with a small recording box after a doctor has requested monitoring over a 24-hour period.
However, as this can cause sleep disturbance, there remain concerns this may not provide realistic nocturnal measurements.
In recent years home blood pressure monitoring (HBPM) has become a more realistic option for accurately checking nocturnal blood pressure as newer, more discreet, BP devices are overcoming these limitations and mean there is minimal sleep disturbance.
Nocturnal Hypertension
Hypertension is a major independent risk factor for cardiovascular diseases, including cardiac death, coronary heart disease, heart failure, stroke, and chronic kidney disease, meaning early diagnosis, prevention and optimal management of hypertension is essential.
BP variation over 24 hours normally follows a pattern, with a peak in the early morning hours and a decrease at night, known as dipping.
In recent years, it has been indicated that nocturnal BP is a better predictor of the risk of cardiovascular events than daytime BP in hypertensive and renal transplant patients. Experts say that nighttime blood pressure readings are a more accurate measurement of a person’s circulatory health.
Patient-management strategies
In addition, nocturnal hypertension can occur even among people whose daytime blood pressure is normal but it is difficult to diagnose because routine blood pressure checks are almost always done during the day.
People who have nocturnal hypertensionare more likely to experience heart failure and other forms of cardiovascular disease, according to a study published in the journal Circulation, with the authors pointing to their research as highlighting the importance of including nighttime blood pressure monitoring in patient-management strategies.
Another study showed that nocturnal systolic BP (SBP) measured by a home BP monitoring device was a significant predictor of cardiovascular disease events, independent of office and morning home SBP levels.
Hence, there is an unmet need for obtaining high quality BP values during sleep.
Smart ring
In the last two decades, technological development of home BP devices as henabled automated BP measurements during night-time with more discreet devices having less impact on a patient’s sleep and, thus, being more likely to provide more accurate nocturnal blood pressure measurements.
Sky Labs’ CART smart ring is capable of round-the-clock blood pressure monitoring. Using photoplethysmography (PPG) signals to measure the bloodstream 24/7 through the wearer’s finger, a new feature of the medical device enables it to constantly monitor hypertension without user intervention and overcoming limitations of existing methods.
Sky Labs is currently running a clinical study on the use of the smart ring for BP monitoring, with results due to be published early next year for continuous blood pressure monitoring, but the CART platform has already proved effective in long-term continuous monitoring for Atrial Fibrillation with accuracy of 96.9%.