From the Guidelines
Blood pressure measurements from watches are generally less accurate than traditional methods like arm cuffs. Most smartwatches use optical sensors that detect blood flow changes rather than directly measuring pressure, leading to potential inaccuracies 1. Factors like movement, positioning, skin tone, and temperature can affect readings. For reliable blood pressure monitoring, use a validated upper arm cuff device that follows established measurement protocols. Wrist-based devices may be useful for tracking trends over time but shouldn't replace clinically validated methods for diagnosis or medication adjustments.
Some key points to consider when evaluating the accuracy of blood pressure measurements from watches include:
- The type of monitor used: oscillometric devices that record pressure from the brachial artery are generally more accurate than wrist or finger devices 1
- The validation of the device: only a few devices have been subjected to proper validation tests such as the AAMI and BHS protocols, and of those, only a few have passed 1
- The individual patient: the fact that a device has passed a validation test does not guarantee accuracy in the individual patient, and it is essential that each device be checked on each patient before the readings are accepted as being valid 1
If you're concerned about your blood pressure, establish a baseline with a medical-grade device and consult your healthcare provider before making health decisions based solely on smartwatch readings. The technology is improving, but current watch-based measurements should be considered approximate rather than definitive values. It's also important to note that home-monitoring devices should be checked for accuracy every 1 to 2 years 1.
From the Research
Accuracy of Blood Pressure Measurement
- The accuracy of blood pressure (BP) measurement is crucial for the diagnosis and management of hypertension 2.
- Studies have shown that BP measurement can be affected by various factors, including the type of device used, the technique employed, and the environment in which the measurement is taken 3, 2.
Validation of Blood Pressure Monitors
- It is essential to use validated BP monitors to ensure accurate measurements 4.
- Consumers can check the validation status of a BP monitor by searching online listings of validated devices 4.
- Only properly validated automatic sphygmomanometers should be used, and practices should perform regular in-house checks of sphygmomanometers 3.
Comparison of Measurement Methods
- Different methods of BP measurement, such as clinic, home, and ambulatory monitoring, have varying degrees of accuracy and clinical utility 2, 5.
- Home BP monitoring and 24-hour ambulatory BP monitoring have been shown to provide more accurate predictions of cardiovascular risk than clinic measurements alone 5, 6.
- The use of home BP measurement can improve measurement precision and reproducibility, and has been found to have better prognostic accuracy than office BP measurement 6.
Factors Affecting Measurement Accuracy
- Factors such as the type of device used, the technique employed, and the environment in which the measurement is taken can affect the accuracy of BP measurement 3, 2.
- Automatic electronic sphygmomanometers can produce systematic errors in some patients, and aneroid sphygmomanometers should be calibrated every 6 months 3.
- The use of validated and calibrated devices, as well as proper training of technicians and healthcare providers, is critical for obtaining accurate BP measurements 2.