Table 1.
Descriptive Characteristics by WASO Quartile (Quartile I: <30.0min; Quartile II: 30.0min–48.5min; Quartile III:49.0min-80.0min; Quartile IV: >80.0min)
| Characteristics | Total (n=4204) | WASO (Min) | ||||
|---|---|---|---|---|---|---|
| First Quartile (n=1048) | Second Quartile (n=1063) | Third Quartile (n=1047) | Fourth Quartile (n=1046) | P value | ||
| Age, year | 63.8±11.1 | 59.2±11.0 | 61.7±10.6 | 65.5±10.3 | 68.7±10.2 | <0.001 |
| Gender, n (%) | <0.001 | |||||
| Male | 1978 (47.1) | 405 (38.6) | 470 (44.2) | 537 (51.3) | 566 (54.1) | – |
| Female | 2226 (52.9) | 643 (61.4) | 593 (55.8) | 510 (48.7) | 480 (45.9) | – |
| Body mass index, kg/m2 | 28.2±5.0 | 28.2±5.2 | 28.0±4.9 | 28.4±4.8 | 28.4±5.0 | 0.122 |
| Race, n (%) | 0.076 | |||||
| White | 3668 (87.3) | 907 (86.5) | 919 (86.5) | 938 (89.6) | 904 (86.4) | – |
| Other | 536 (12.7) | 141 (13.5) | 144 (13.5) | 109 (10.4) | 142 (13.6) | – |
| Smoking status, n (%) | 0.044 | |||||
| Smoker | 2260 (53.8) | 546 (52.1) | 549 (51.7) | 568 (54.3) | 597 (57.2) | – |
| Never smoker | 1938 (46.2) | 502 (47.9) | 512 (48.3) | 478 (45.7) | 446 (42.8) | – |
| Alcohol use, n (%) | 0.170 | |||||
| At least 1 drink per day | 1708 (43.3) | 419 (42.9) | 457 (45.9) | 399 (41.0) | 433 (43.3) | – |
| None | 2238 (56.7) | 557 (57.1) | 538 (54.1) | 575 (59.0) | 568 (56.7) | – |
| Benzodiazepine use, n (%) | 246 (5.9) | 48 (4.6) | 65 (6.1) | 59 (5.6) | 74 (7.1) | 0.105 |
| Diabetes mellitus, n (%) | 295 (7.0) | 55 (5.2) | 53 (5.0) | 93 (8.9) | 94 (9.0) | <0.001 |
| Hypertension, n (%) | 1681 (40.0) | 309 (29.5) | 382 (35.9) | 447 (42.7) | 543 (51.9) | <0.001 |
| AHI, events/h | 9.9±13.0 | 7.8±11.2 | 8.9±12.2 | 10.3±12.5 | 12.5±15.4 | <0.001 |
| Sleep duration, h | 7.3±0.9 | 7.0±1.0 | 7.2±0.9 | 7.4±0.9 | 7.7±0.8 | <0.001 |
| SE, % | 83.4±10.0 | 91.6±5.5 | 88.0±4.5 | 82.7±4.9 | 71.1±9.5 | <0.001 |
| REM, % | 19.7±6.8 | 21.3±6.6 | 20.3±6.3 | 19.3±6.7 | 17.8±7.1 | <0.001 |
| SWS, % | 17.5±11.9 | 19.9±12.1 | 18.3±11.4 | 15.9±11.5 | 16.0±12.2 | <0.001 |
| SL, min | 12.8±19.5 | 14.0±21.5 | 12.4±18.6 | 12.7±18.5 | 12.2±19.2 | 0.177 |
| Total ArI, events/h | 19.0±10.4 | 15.4±8.6 | 18.0±8.8 | 20.1±10.0 | 22.7±12.3 | <0.001 |
| ArI-REM, events/h | 15.2±10.8 | 13.7±10.0 | 15.0±10.6 | 15.3±10.2 | 16.7±12.3 | <0.001 |
| ArI-NREM, events/h | 19.9±11.3 | 15.8±9.3 | 18.7±9.5 | 21.2±11.2 | 24.0±13.3 | <0.001 |
| SFI, events/h | 8.9±3.4 | 7.4±2.6 | 8.5±2.8 | 9.0±3.0 | 10.5±4.2 | <0.001 |
| Follow-up time, year | 10.7±3.0 | 11.2±2.7 | 11.0±2.8 | 10.7±2.9 | 10.0±3.4 | <0.001 |
Notes: Results are presented as mean ± standard deviation or n (%). The P values represent the difference among four groups.
Abbreviations: AHI, apnea hypopnea index; ArI, arousal index; NREM, non-rapid eye movement; REM, rapid eye movement; SFI, sleep fragmentation index; SL, sleep latency; SWS, slow wave sleep; WASO, wake after sleep onset.