Validity of diurnal sleep recording in the diagnosis of sleep apnea syndrome.

Two polysomnographic studies were performed in 35 subjects who had a clinical suspicion of sleep apnea syndrome: one study was done at night (N) (from 10:00 p.m. to 8:00 a.m.) and the other during the day (D) starting after lunch (from noon to 5:00 p.m.). N and D sleep studies were performed in random order at a minimal interval of 36 h. No treatment (drug, CPAP) was initiated between the two studies. Both studies included the recording of sleep stages (EEG, EOG, EMG), nasal and mouth flows, thoracoabdominal movements, electrocardiogram, and SaO2 (ear oximetry). D sleep was present in all but one subject. As expected, the total sleep time (TST) was significantly shorter during the D than during the N study (2.6 +/- 0.2 and 6.2 +/- 0.2 h, respectively, mean +/- SEM, p less than 0.001, Wilcoxon's signed-rank test). Stages III-IV and REM were significantly less represented during the D (13.1 +/- 2.4 and 7.7 +/- 1.3%, respectively) than during the N study (18.5 +/- 1.7 and 15.3 +/- 0.8%, p less than or equal to 0.005). From the results of the N study, the diagnosis of sleep apnea syndrome (apnea index greater than 5 and/or apnea + hypopnea index greater than 10) was made in 25 patients, and it was confirmed by the same criteria in 22 by the D sleep recording. There was a significant correlation between the N and D values for these indices (r greater than or equal to 0.9, p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)