Sleep and vigilance
| Healthy lowlanders LL group | Healthy highlanders HH group | Highlanders with HAPH HAPH+ group | |
| Subjects n | 34 | 54 | 36 |
| Total AHI events·h−1 | 4.3 (1.4–12.6) | 9.0 (3.6–16.0) | 33.8#,¶ (26.9–54.6) |
| Obstructive AHI events·h−1 | 3.7 (0.4–11.8) | 5.1 (1.8–13.3) | 24.6#,¶ (15.4–52.8) |
| Central AHI events·h−1 | 0.6 (0.1–1.2) | 1.4# (0.8–3.6) | 5.2#,¶ (2.3–9.3) |
| Mean nocturnal SpO2 % | 96 (95–97) | 90# (88–92) | 87#,¶ (84–88) |
| Time with SpO2 <90% %TIB | 0 (0–0) | 33# (10–69) | 78#,¶ (61–89) |
| ODI (>3%) events·h−1 | 1.6 (0.9–6.7) | 7.2# (3.6–19.5) | 32.4#,¶ (20.6–56.5) |
| PtcCO2 in NREM sleep kPa | 5.7 (5.2–6.1) | 5.5 (4.9–5.7) | 5.6 (4.8–6.1) |
| PtcCO2 in REM sleep kPa | 5.7 (5.3–6.3) | 5.5 (5.1–5.9) | 5.7 (5.0–6.3) |
| Total sleep time min | 449 (399–498) | 432 (404–481) | 407# (357–444) |
| Sleep efficiency % TIB | 86 (76–89) | 83 (75–89) | 78#,¶ (67–82) |
| WASO min | 44 (20–90) | 72# (42–111) | 104#,¶ (78–130) |
| Sleep latency min | 17 (12–32) | 17 (11–43) | 16 (10–35) |
| NREM sleep stages 1+2 %TST | 54 (50–63) | 59# (53–66) | 63#,¶ (59–67) |
| NREM sleep stages 3+4 %TST | 24 (19–31) | 22 (18–26) | 22 (13–24) |
| REM sleep %TST | 20 (17–23) | 18# (13–21) | 17# (12–21) |
| Arousal index events·h−1 | 9.8 (7.0–14.9) | 9.6 (5.9–12.1) | 10.1 (7.7–16.5) |
| Heart rate min−1 | 61 (55–69) | 65 (59–72) | 75#,¶ (69–79) |
| Premature ventricular beats during TIB events·h−1 | 0.0 (0.0–0.0) | 0.0 (0.0–0.0) | 0.0#,¶ (0.0–1.03) |
| PVT reaction time ms | 237 (217–323) | 347# (277–418) | 384#,¶ (329–596) |
| Trail making test s | 85 (73–111) | 121# (103–146) | 156#,¶ (134–177) |
| Estimated night-time spent awake min | 10 (5–20) | 20# (10–60) | 30# (10–53) |
| Subjective sleep quality visual analogue score+ | 50 (43–78) | 61 (46–76) | 50 (41–66) |
Data are presented as median (interquartile range), unless otherwise stated. AHI: apnoea–hypopnoea index; SpO2: arterial oxygen saturation measured by pulse oximetry; TIB: time in bed; ODI: oxygen desaturation index; PtcCO2: transcutaneous carbon dioxide tension; WASO: wakefulness after sleep onset; NREM: non-rapid eye movement; TST: total sleep time; REM: rapid eye movement; PVT: psychomotor vigilance test. #: p<0.05 versus healthy lowlanders; ¶: p<0.05 versus healthy highlanders; +: the range of the sleep quality visual analogue score was from 0 (extremely poor) to 100 (excellent).