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One Third of Patients with Obstructive Sleep Apnoea-Hypopnoea Syndrome May Have White Coat Hypertension

White coat hypertension (WCH), seen when patients have a high blood pressure (BP) when measured in the physician's office but are normotensive elsewhere, may be a frequent occurrence in patients with obstructive sleep apnoea-hypopnoea syndrome (OSAHS), according to a recent study. This finding may indicate the overdiagnosis of hypertension in one-third of these patients.

Ninety-six consecutive patients with OSAHA were seen by Francisco Garcia-Rio, PhD, and colleagues from the Hospital Universitario La Paz in Madrid, Spain. Twenty healthy subjects were used as controls. Antihypertensive treatments were discontinued at least 3 weeks before the examination and subjects were asked not to eat for 4 hours, not smoke at least 2 hours or drink caffeinated or alcoholic beverages for at least 12 hours before the study.

Twenty-four-hour ambulatory BP monitoring (ABPM) was performed on each patient. Office BPs were measured using a random 0 sphygmomanometer with the subject sitting for at least 5 minutes. The diagnosis of hypertension was based on the mean of 3 readings obtained at 2 separate visits and based on World Health Organization (WHO) criteria. The existence of a nocturnal decrease in BP of greater than or equal to 10%, defined "dipper" status.

In addition, blood serum was tested for cholesterol, triglycerides and glucose. Urine samples were obtained from 8 am to 11 pm (diurnal) and 11 pm to 7 am (nocturnal), and excretion of norepinephrine and epinephrine were determined. The patients also underwent polysomonography testing overnight.

Office hypertension was seen in 45 patients with OSAHS, according to the WHO standards. After ABPM, hypertension was confirmed in 30 patients with OSAHS (sustained hypertensives) and not found in the remainder (WCH). The frequency of WCH was 33%.

There were no significant differences in age, sex, body mass index (BMI), or smoking habits between the two groups and controls. Metabolic parameters were also similar. Those with WCH had statistically significant higher values for onset of sleep onset latency, wake-after-sleep-onset, and "dipper" status. No other areas in sleep characteristics, lung function data, or urinary catecholamines were found to be significant.

"This study, the first to our knowledge to analyze the WCH phenomenon in patients with OSAHS, showed that one third of these patients, diagnosed hypertensive with office BP measurements, presented with WCH," said Dr. Garcia-Rio. "This could lead to an overdiagnosis among these subjects."


Chest 2004 Mar;125:817-822. "White coat hypertension in patients with obstructive sleep apnea-hypopnea syndrome"

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