STUDY OBJECTIVE: To investigate the short-term effect (4 weeks) of oral appliance therapy for obstructive sleep apnea on blood pressure. DESIGN: Randomized, controlled, crossover trial.

SETTING: Multidisciplinary sleep disorders clinic in a university teaching hospital.

PATIENTS: Sixty-one patients diagnosed with obstructive sleep apnea on polysomnography (apnea hypopnea index > or = 10 per hour and at least 2 of the following symptoms--daytime sleepiness, snoring, witnessed apneas, fragmented sleep; age > 20 years; and minimum mandibular protrusion of 3 mm).

INTERVENTION: A mandibular advancement splint (MAS) and control oral appliance for 4 weeks each.

MEASUREMENTS AND RESULTS: Polysomnography and 24-hour ambulatory blood pressure monitoring were carried out at baseline and following each 4-week intervention period. Patients showed a 50% reduction in mean apnea hypopnea index with MAS compared with the control and a significant improvement in both minimum oxygen saturation and arousal index. There was a significant reduction with the MAS in mean (+/- SEM) 24-hour diastolic blood pressure (1.8 +/- 0.5 mmHg) compared with the control (P = .001) but not in 24-hour systolic blood pressure. Awake blood-pressure variables were reduced with the MAS by an estimated mean (+/- SEM) of 3.3 +/- 1.1 mmHg for systolic blood pressure (P = .003) and 3.4 +/- 0.9 mmHg for diastolic blood pressure (P < .0001). There was no significant difference in blood pressure measured asleep.

CONCLUSION: Oral appliance therapy for obstructive sleep apnea over 4 weeks results in a reduction in blood pressure, similar to that reported with continuous positive airway pressure therapy.