Polysomnographic characteristics of OSA clusters (ranked by AHI, A–G) grouped according to domain (breathing disturbance, hypoxaemia, sleep architecture disturbance and autonomic dysregulation)*
| Cluster/variable |
(A) Mild |
(B) PLMS |
(C) NREM and poor sleep |
(D) REM and hypoxia |
(E) Hypopnoea and hypoxia |
(F) Arousal and poor sleep |
(G) Combined severe |
| N | 533 | 119 | 186 | 168 | 75 | 42 | 124 |
| Mean±SD or median (IQR) | |||||||
| AHI | 3.6 (9.0) | 9.9 (18.6) | 19.3(30.6) | 18.9(24.5) | 44.2 (39.0) | 67.8 (30.4) | 83.9 (28.0) |
| Breathing disturbance | |||||||
| Total apnoea index | 3.9 (5.5) | 5.0 (11.6) | 13.0 (26.2) | 13.5 (18.3) | 13.8 (22.3) | 61.6 (29.4) | 77.9 (28.9) |
| Total hypopnoea Index | 3.0 (12.8) | 6.0 (16) | 4.0 (11.0) | 7.0 (17.0) | 32.0 (51.0) | 3.5 (11.0) | 1.0 (6.0) |
| % Obstructive apnoeas | 66±37 | 79±29 | 82±29 | 89±17 | 89±24 | 87±24 | 80±26 |
| % Combined apnoeas | 46±33 | 49±31 | 58±31 | 55±26 | 63±26 | 32±22 | 81±20 |
| % Apnoeas with arousal only | 32±34 | 32±33 | 30±30 | 18±22 | 9±17 | 65±23 | 7±9 |
| REM: NREM apnoea ratio | 3.4±7.5 | 2.3±5.3 | 0.8±3.6 | 8.1±15.7 | 0.3±1.1 | 0.1±0.4 | 0.1±0.2 |
| Apnoea D4: apnoea arousal ratio | 1.4±4.1 | 1.2±2.7 | 0.8±1.6 | 3.1±4.3 | 7.2±10.8 | 0.1±0.1 | 4.4±8.4 |
| Hypoxaemia | |||||||
| T<90% O2 Index | 0.00 (0.02) | 0.02 (0.10) | 0.01 (0.10) | 0.09 (0.23) | 0.14 (0.36) | 0.00 (0.04) | 0.20 (0.41) |
| >4% Desaturation index | 4.1 (8.8) | 8.7 (15.1) | 18.5 (24.8) | 19.8 (22.0) | 57.1 (37.5) | 21.0 (41.1) | 74.2 (30.1) |
| Lowest nocturnal O2 % saturation | 86.1±4.2 | 82.7±6.7 | 84.7±5.0 | 72.8±7.6 | 78.8±6.8 | 87.1±4.2 | 77.7±7.0 |
| Sleep architecture disturbance | |||||||
| Sleep efficiency | 77.7±14.5 | 69.8±17.5 | 54.7±17.9 | 79.6±13.6 | 68.2±16.7 | 56.4±22.8 | 68.8±16.6 |
| Stage 1 % | 15.2 (8.9) | 21.1 (12.2) | 40.9 (20.3) | 16.5 (10.7) | 23.2 (15.4) | 40.8 (23.4) | 40.6 (25.4) |
| Stages 3 and 4 % | 1.5 (8.4) | 0.2 (4.8) | 0.0 (0.0) | 0.0 (6.6) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) |
| REM % | 12.0 (12.7) | 6.4 (14.0) | 0.0 (6.4) | 12.3 (10.6) | 0.0 (2.7) | 0.0 (0.0) | 0.0 (0.0) |
| Stage shift index | 23.8±10.2 | 27.3±12.2 | 47.9±23.1 | 24.7±12.4 | 33.1±18.2 | 57.3±29.1 | 45.4±28.0 |
| Autonomic dysregulation | |||||||
| Total arousal index | 25.9±12.1 | 40.7±21.5 | 65.1±23.6 | 37.3±19.8 | 60.1±25.0 | 88.5±27.4 | 91.7±27.3 |
| % Spontaneous arousals | 66±22 | 43±20 | 50±21 | 43±23 | 28±16 | 19±11 | 13±10 |
| PLMS index | 0.0 (6.2) | 64.7 (32.3) | 0.0 (7.6) | 0.0 (4.9) | 0.0 (0.0) | 0.0 (0.0) | 0.0 (0.0) |
Note: Each of the variables exhibits statistically significant differences across clusters (analysis of variance, all p values <0.001).
Bold cells denote variables differentiating the clusters within the same category of OSA severity (none/mild (AHI <15), moderate (15≤AHI<30) and severe (AHI ≥30)).
*The above variables are provided for cluster interpretation purposes and clinical familiarity. Feature values used to generate clusters A through G using cluster analysis are provided in online supplementary file.
>4% desaturation index, number of 4% desaturations/total sleep time; AHI, apnoea–hypopnoea index (events/hour of total sleep time); apnoea D4, apnoea with 4% desaturation only and no arousal; apnoea arousal, apnoea with arousal only and no desaturation; combined apnoea, apnoea with 4% desaturation and arousal; NREM, non-rapid eye movement; REM, rapid eye movement; OSA, obstructive sleep apnoea; PLMS, periodic limb movements of sleep; T<90% O2 index, time spent at O2 saturation < 90%/total sleep time; total hypopnoea, hypopnoea with 4% desaturation with or without arousal.