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 there’s an opposite phenomenon, known as “masked hypertension”, where a person’s 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 people’s 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 doctor’s 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 people’s 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 people’s blood pressure in the future.