'White coat hypertension' common among sleep apnea patients
March 15, 2004
NORTHBROOK, Ill. - Patients with sleep apnea may be commonly misdiagnosed with hypertension, says a study published in the March issue of CHEST, the peer-reviewed journal of the American College of Chest Physicians.
In the study, one-third of patients with sleep apnea who were physician-diagnosed with hypertension actually had "white coat hypertension,” a condition characterized by an increase in blood pressure during a doctor's office visit and normal blood pressure during all other situations. The study also found that patients with sleep apnea and WCH had a more difficult time falling asleep and had longer periods of wakefulness after falling asleep than sleep apnea patients with normal blood pressure or sustained high blood pressure.
"Although the relationship between hypertension and sleep apnea is well established, our results suggest that the occurrence of WCH could lead to overdiagnosis of hypertension among patients with sleep apnea, thereby leading to potentially flawed conclusions regarding the causative association of hypertension and sleep apnea," said lead researcher Francisco Garcia-Rio, PhD, La Paz University Hospital, Madrid, Spain.
Researchers from La Paz University Hospital observed the frequency of WCH in patients with sleep apnea and the characteristics of patients with both conditions. Ninety-nine patients with sleep apnea and 20 healthy patients (control group) were included in the study. Of the patients with sleep apnea, 45 patients were physician-diagnosed with hypertension, and the remaining patients were considered to have normal blood pressure levels.
During a 24-hour period, all patients underwent regular intervals of ambulatory blood pressure monitoring, polysomnography, and blood and urine testing. Results showed that in patients with sleep apnea initially diagnosed with hypertension, 30 patients were confirmed to have sustained hypertension, while the remaining 15 patients had normal blood pressure readings. All other patients presented normal blood pressure readings.
Further analysis revealed that patients with WCH took three times as long to fall asleep and had longer periods of wakefulness after sleep onset than patients with sustained hypertension. No other differences in sleep characteristics, lung function data, or urinary hormone levels were found between the groups with sleep apnea. In addition, there were no significant differences in gender, age, body mass index, or smoking habits between sleep apnea and control groups.
"The medical community should be cautious in utilizing these data in clinical practice, since it is preliminary in nature. However, the potential importance of sleep apnea as a secondary or correctable cause of hypertension should alert the clinicians in pursuing the diagnosis of sleep apnea, especially in patients in whom blood pressure can not be controlled medically," said the author of a corresponding editorial, Hector O. Ventura, MD, Cardiomyopathy and Heart Transplantation Center, Ochsner Clinical Foundation, New Orleans, La.