Some people with normal blood pressure have elevated blood pressure when their doctor takes the reading. This phenomenon is known as white coat hypertension. But theres an opposite phenomenon, known as masked hypertension, where a persons blood pressure is normal in a clinical setting, but high the rest of the time. Until now, it has not been clear how prevalent this problem is. A new study by Stony Brook University and Columbia University in New York, however, found that out of a sample of about 888 people nearly 16% had masked hypertension.
People with high blood pressure have an increased risk of suffering from a stroke, heart attack or developing kidney disease, so the ability to accurately measure peoples blood pressure is very important. We have known for many years that 24-hour blood pressure monitoring is more accurate in predicting the risk of having a heart attack or stroke than a one-off measurement at a doctors surgery. Twenty-four hour monitoring is done with an portable (ambulatory) monitor which takes blood pressure readings every 15 to 30 minutes. These readings are then averaged to give a more accurate assessment of whether someone has hypertension (high blood pressure) or not.
Through the increased use of 24-hour monitoring of peoples blood pressure and the efforts of clinical scientists, the extent of this hidden public health problem is being uncovered. Many people who are considered healthy as a result of having their blood pressure recorded as normal by a healthcare professional, actually have undiagnosed and untreated hypertension.
The researchers at Stony Brook University showed that the differences between the clinic and 24-hour measurement of blood pressure was dependent on the age and body mass index of the people being assessed. They showed that the younger people in the study who were of normal weight had higher levels of masked hypertension compared with the older more overweight people. This is an important point for doctors to consider when attempting to accurately identify and measure different peoples blood pressure in the future.
This new study overlaps with the clinical health research our vascular physiology research group is undertaking at Cardiff Metropolitan University. Our group is investigating the link between 24-hour blood pressure and heart function, and brain and kidney blood flow in the general population. As a result of this latest research paper, the information provided has highlighted the importance of routinely measuring 24-hour blood pressure as part of our research work. It will be important for our work to identify people with masked hypertension and understand the impact high blood pressure may have on organs like the brain, eyes and kidneys.
Stress of everyday living
Stresses and pressures associated with everyday living have been proposed as the reasons people may develop masked hypertension. It may be that only through measuring 24-hour blood pressure can masked hypertension be identified.
Some employers offer work-place health assessments, including 24-hour blood pressure monitoring. These sorts of initiatives are invaluable for identifying people with masked hypertension. In addition to identifying the problem, organisations need to put strategies in place to help people deal with stress, manage their blood pressure and reduce their cardiovascular risk.