Hypertension is a major risk factor for cardiovascular disease. However, more than half of adults with high blood pressure are unaware of their condition. Wearable devices could help identify these individuals, but their sensors are not yet accurate enough for direct blood pressure measurement and require calibration using a standard blood pressure monitor.
A team of scientists has developed a system that assesses the risk of hypertension without any pre-setting. It analyzes two types of signals collected by Google's smartwatch: photoplethysmography (photoplethysmography), which measures changes in blood volume in the vessels beneath the skin, and accelerometer data, which records wrist movements. The algorithm also takes into account a person's height. Several measurements over a period of time are required to assess the risk.
The researchers first trained the system on nearly 500,000 hours of data collected from 2,109 people. They then tested it in a study involving 196 people without known cardiovascular disease who were not taking hypertension medication. Participants wore the watch for seven days, and the algorithm's results were compared with 24-hour ambulatory blood pressure monitoring—the clinical reference method.
The smartwatch-based system detected hypertension with a sensitivity of 65.8%. For the initial blood pressure measurement in the doctor's office, the sensitivity was 55.3%. The difference between the results was not statistically significant. The specificity of both methods was the same—90%, meaning they were equally effective at ruling out hypertension in people without the condition.
The authors also assessed the positive predictive value—the probability that a person actually has hypertension if the test results are positive. For the smartwatch, it was 80.6%, compared to 77.8% for in-office testing. Thus, the wearable device demonstrated comparable results to the traditional primary screening method, although the study currently involves a relatively small group of participants.
Researchers emphasize that smartwatches will not replace medical blood pressure monitors. Signs of hypertension detected by wearable devices must be confirmed using standard methods. However, this technology could become an additional tool for mass screening, helping to identify at-risk individuals and refer them for testing before serious complications arise.
