Sleep apnea syndrome and essential hypertension.

More than half of patients with essential hypertension have sleep apnea. The incidence of unrecognized sleep apnea in patients with essential hypertension was assessed. Twenty-three patients taking antihypertensive medication were selected at random from a hypertension clinic. They were evaluated by questionnaire for symptoms of sleep apnea, and during 3 hours of sleep, measurements were made of respiratory patterns using an impedance pneumograph, arterial O2 saturation with an ear oximeter and air flow at the mouth or nose with a face mask pneumotacograph. Abnormal sleep apneas (average 20 seconds) lasting for an average of 19% sleep time were found in 11 patients (48%). Significant arterial O2 desaturation, defined as a decrease of at least 4% and to less than 90%, was observed in 7 of these 11 (30%), with an average saturation of 87% at the end of the apneic episodes. Thus, almost one-third of patients randomly selected had significant arterial O2 desaturation during sleep because of sleep apnea, and it is suggested that sleep apnea may play a part in the development of essential hypertension.