Table 1.
Demographic, clinical characteristics and sleep study results
| Characteristics | Sleep apnoea (n=513) |
Non-sleep apnoea (n=494) |
P value |
| Age, median (IQR), years | 62 (56–68) | 61 (56–67) | 0.23 |
| Male sex, n (%) | 442 (86.2) | 429 (86.8) | 0.75 |
| Ethnicity, n (%) | 0.37 | ||
| Chinese | 338 (65.9) | 314 (63.3) | |
| Malay | 93 (19.1) | 101 (20.4) | |
| Indian | 50 (9.7) | 57 (11.5) | |
| Others | 32 (6.2) | 22 (4.5) | |
| Clinical measurements | |||
| Systolic blood pressure, mean (SD), mm Hg | 125 (111–138) | 125 (110–138) | 0.70 |
| Diastolic blood pressure, mean (SD), mm Hg | 70 (63–79) | 70 (62–79) | 0.35 |
| Body mass index, mean (SD), kg/m2 | 25.9 (23.3–28.6) | 23.5 (21.8–26.2) | <0.0001 |
| Neck circumference, mean (SD), cm | 39 (37–41) | 38 (36–40) | <0.0001 |
| Waist circumference, mean (SD), cm | 95 (88–102) | 90 (84–96) | <0.0001 |
| Cardiovascular risk factors, n (%) | |||
| Smoking | 139 (27.1) | 155 (31.4) | 0.23 |
| Hyperlipidaemia | 401 (81.2) | 417 (81.3) | 0.96 |
| Hypertension | 404 (78.8) | 349 (70.6) | 0.0030 |
| Diabetes mellitus | 295 (57.5) | 278 (56.3) | 0.69 |
| Family history of premature coronary disease | 37 (7.2) | 43 (8.7) | 0.38 |
| Concomitant conditions, n (%) | |||
| Previous myocardial infarction | 239 (46.6) | 221 (44.7) | 0.56 |
| Previous percutaneous coronary intervention | 119 (23.2) | 101 (20.4) | 0.29 |
| Previous coronary artery bypass surgery | 0 (0.0) | 2 (0.4) | 0.24* |
| Stroke/transient ischaemic attack | 61 (11.9) | 57 (11.5) | 0.86 |
| Chronic kidney disease† | 102 (19.9) | 63 (12.8) | 0.002 |
| Chronic kidney disease on dialysis | 28 (5.5) | 8 (1.6) | 0.001* |
| Pre-existing atrial fibrillation | 24 (4.7) | 23 (4.3) | 1.00* |
| Pacemaker in situ | 2 (0.4) | 1 (0.2) | 1.00* |
| Implantable cardioverter defibrillator in situ | 3 (0.6) | 1 (0.2) | 0.63* |
| Sleep study results | |||
| AHI (events per hour), median (IQR) | 30.1 (20.6–44.7) | 5.85 (3.0–10.23) | <0.0001 |
| RDI (events per hour), median (IQR) | 32.9 (24.3–47.4) | 10.4 (6.6–14.4) | <0.0001 |
| ODI (events per hour), median (IQR) | 18.1 (11.2–33.6) | 2.3 (0.9–4.83) | <0.0001 |
| Sleep duration (hour), median (IQR) | 6.40 (5.49–7.30) | 6.30 (5.32–7.10) | 0.24 |
| Duration SpO2<90% (min), median (IQR) | 4.50 (0.60–19.85) | 0.00 (0.00–0.60) | <0.0001 |
| Percentage of sleep SpO2<90% (%), median (IQR) | 1.20 (0.20–5.08) | 0.00 (0.00–0.10) | <0.0001 |
| Epworth Sleepiness Scale >10, n (%) | 69 (13.5) | 54 (11.0) | 0.23 |
| High-risk Berlin Questionnaire, n (%) | 239 (46.8) | 201 (40.9) | 0.06 |
*P values were computed using Fisher’s exact test.
†Serum estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2.
AHI, apnoea-hypopnoea index; ODI, oxygen desaturation index; RDI, respiratory disturbance index; SpO2, arterial oxygen saturation.