[Severity of obstructive sleep apnea syndrome relates to sleep architecture changes]

To explore how obstructive sleep apnea syndrome (OSAS) affects sleep architecture and if OSAS severity and treatment relate to it.

A computer-assistant diagnostic system was used for polysomnography(PSG) recording. Respiratory events were scored automatically and corrected manually. Sleep was scored manually according to the standard set by Rechtschaffen. 31 controls and 147 OSAS patients(RDI > or = 5) were defined by PSG. 11 OSAS patients(RDI = 62.5 +/- 20.8) accepted nCPAP therapy. PSG were recorded both before and during nCPAP treatment.

(1) Compared with controls, OSAS group had increased sleep shift number (120 +/- 71 vs 92 +/- 60, P = 0.0106); (2) The number of slow wave sleep(SWS) (5 +/- 9 vs 8 +/- 8, P = 0.0035) and the ratio of total SWS time over total sleep time(TST) (5% +/- 8% vs 8% +/- 9%, P = 0.0062), were decreased and the rate of SWS deprivation(48% vs 26%, P < 0.05) were increased greatly in OSAS patients; (3) REM were less affected by OSAS than SWS because the ratio of its total time over TST, its onset number and deprivation rate had no significant difference between the two groups; (4) OSAS group had increased number of WASO (wake after sleep onset) (27 +/- 28 vs 19 +/- 18, P = 0.017) but the ratio of total WASO time over total sleep period had no significant difference between the two groups; (5) The ratio of total RWS(rapid wave sleep) time over TST (94 +/- 10 in OSAS group vs 91 +/- 12, P = 0.0136) and total RWS number(88 +/- 54 in OSAS group vs 65 +/- 45, P = 0.0075) were increased in OSAS group; (6) The above parameters were obviously disturbed in OSAS patients with RDI > or = 25 but had almost no change in patients with RDI < 25 compared with controls. (7) nCPAP could improve the above parameters but only number of WASO(no therapy: 34 +/- 20 vs therapy: 23 +/- 22, P = 0.011), shift number (no therapy: 151 +/- 62 vs therapy: 97 +/- 50, P = 0.019) and the ratio of total RWS time over TST (no therapy: 115 +/- 58 vs therapy: 69 +/- 34, P = 0.025) had statistical significance.

OSAS severity relates to sleep architecture changes. Those had RDI < 25 had no change compared with control group. Sleep architecture changes could be improved by effective nCPAP therapy.