Patients with "masked" hypertension that is not detected by routine office blood pressure measurements appear to have stroke and death rates similar to that of patients with sustained high blood pressure; whereas patients with so-called "white coat" hypertension appear to have no greater risk than people with normal blood pressure, according to a new study in the Aug. 2, 2005, issue of the Journal of the American College of Cardiology.
"It is important for physicians and other health practitioners to recognize at least the possibility that conventional blood pressure measurements could miss masked hypertension. Otherwise, they may not suspect masked hypertension if a patient develops organ damage or cardiovascular diseases in spite of good control of blood pressure and other risk factors according to measurements taken in the office. If these patients are not identified and do not receive appropriate treatment, they could develop further organ damage or cardiovascular problems," said Takayoshi Ohkubo, M.D., Ph.D., at Tohoku University Hospital in Sendai, Japan.
Almost one out of five participants in this study had masked hypertension; that is, their blood pressure appeared to be normal according to conventional measurements in a clinic, but it was high when measured by a device that was worn by the participant over a 24-hour period.
"White coat" hypertension means that a person’s blood pressure appears high when it is measured during a clinic visit (typically by a physician or nurse in a white coat), but the pressure is lower when measured by the patient outside of the clinic.
This is the first prospective study to reveal the risks associated with masked hypertension and "white coat" hypertension in a representative sample of a general population. The 1,332 participants (872 women and 460 men at least 40 years old) lived in Ohasama, Iwate Prefecture, Japan. In addition to obtaining "casual" blood pressure measurements in typical clinical settings, the study subjects wore ambulatory blood pressure monitors that automatically recorded data over a 24 hour period. Deaths and strokes were tracked for an average of 10 years after the initial blood pressure measurements.
Participants with normal blood pressure (as measured in the clinic and with ambulatory monitoring) or "white coat" hypertension (meaning their clinic measurements were high, but the ambulatory monitor readings were normal) had similar outcomes. However, the risks of stroke or death were significantly higher for both patients with sustained hypertension (elevated both in the clinic and on ambulatory readings) and those with masked hypertension (normal in clinic measurements, but elevated according to ambulatory monitoring).
"Masked hypertension has a poor prognosis, and it may not be identified by conventional blood pressure measurement. The use of ambulatory blood pressure monitoring can identify masked hypertension," Dr. Ohkubo said. "Masked hypertension is a similarly risky condition to sustained hypertension."
Dr. Ohkubo said that ideally every adult should be screened with an ambulatory blood pressure monitor at least once. If universal screening with 24-hour ambulatory monitoring is difficult, he recommended screening individuals who have an elevated risk of cardiovascular disease. Home blood pressure monitors could also be used to help identify patients, he said.
Based on the results of this long-running study, Dr. Ohkubo said individuals with masked hypertension should be treated the same as patients with sustained hypertension. He said individuals with "white coat" hypertension might need blood pressure treatment only if other factors put them at high risk for cardiovascular disease, but he added that they would need to be carefully followed with ambulatory or home blood pressure measurements, since their very long-term prognosis has not been clarified.
The researchers said that randomized, controlled trials and studies of other populations are needed to fully understand the risks and appropriate treatments of masked and "white coat" hypertension.
Franz H. Messerli, M.D., F.A.C.C., at St. Luke’s Roosevelt Hospital Center and Columbia University in New York, who wrote an editorial with Delia Cotiga, M.D., said the results of this study suggest that physicians can be conservative in managing patients with "white coat" hypertension, since it does not appear to greatly elevate the risk of cardiovascular events.
"On the other hand, masked hypertension is a more serious issue. Patients with masked hypertension, as shown in this article, do not have such a good prognosis. They suffer almost as many strokes and heart attacks as patients with untreated hypertension. Therefore, it is extremely important that we do think of masked hypertension and in appropriate situations do a 24-hour ambulatory monitoring in order to find out whether the patient does have masked hypertension," Dr. Messerli said.