Table 2

Demographics and sleep parameters of patients grouped by moderate-to-severe sleep apnoea (AHI ≥15) and CAI ≥5

CharacteristicsAHI <15AHI ≥15CAI <5CAI ≥5
Total number of patients (%)139 (68.1)65 (31.9)171 (83.8)33 (16.2)
Body mass index, mean (SD), kg/m227.8 (5.6)30.2 (7.3)*28.4 (6.3)29 (6.7)
Age, mean (SD), years50 (13)56 (12.4)*52 (13.2)54 (12.7)
Neck circumference, mean (SD), cm37.9 (4.7)40.7 (5.1)**38.6 (5)40 (5.2)
Male sex, n (%)48 (35)36 (55.4)*66 (38.6)18 (54.5)
STOP-Bang score, mean (SD)3.1 (1.5)4.5 (1.5)**3.5 (1.6)3.8 (1.7)
Epworth Sleepiness Scale, mean (SD)7.8 (5.3)9.8 (5.2)*8.2 (5.4)9.8 (5.3)
Daytime SpO2, mean (SD), %95.6 (1.9)94.0 (2.6)**95.5 (1.9)93.3 (3.1)**
MME, median (IQR), mg per 24 hours60 (22.5–148.5)80 (30–188.8)60 (22.5–135)172.5 (50–735)**
Thyromental distance, mean (SD), cm8.6 (1.8)8.7 (2)8.7 (1.8)8.3 (2)
Mallampati score, n, <3 vs ≥374, 6525, 4087, 8412, 21
Cannabis, n (%)11 (7.9)4 (6.2)13 (7.6)2 (6.0)
Medical conditions, n (%)
Active smoker31 (22.3)16 (24.6)39 (22.8)8 (24.2)
Asthma/COPD19 (13.7)6 (9.2)22 (12.9)3 (9.1)
Hypertension18 (12.9)15 (23.1)28 (16.4)5 (15.2)
Cardiovascular diseases†6 (4.3)3 (4.6)8 (4.7)1 (3)
Diabetes11 (7.9)10 (15.4)18 (10.5)3 (9.1)
Osteoarthritis38 (27.3)17 (26.2)44 (25.7)11 (33.3)
Spinal disease24 (17.3)12 (18.5)28 (16.4)8 (24.2)
Neuromuscular disease30 (21.6)17 (26.2)37 (21.6)10 (30.3)
Hypothyroidism14 (10.1)4 (6.2)16 (9.4)2 (6.1)
Gastro-oesophageal reflux disease19 (13.7)8 (12.3)23 (13.5)4 (12.1)
Depression5 (3.6)4 (6.2)9 (5.3)0 (0)
Sleep parameters
AHI, median (IQR), events/hour3.5 (1.3–6.5)33.6 (19.8–54)**5 (1.5–12.7)33.6 (17.1–69.2)**
Obstructive apnoea index, median (IQR), events/hour2.6 (1–5.1)20.4 (14.8–36.7)**4.3 (1.3–12)9.7 (3.7–19.3)*
CAI, median (IQR), events/hour0.2 (0–0.9)2.8 (0.2–15.6)**0.2 (0–0.9)15.6 (9.1–42.1)**
Mixed apnoea index, median (IQR), events/hour0 (0–0)0 (0–0.3)**0 (0–0)0 (0–0.5)**
Hypopnoea index, median (IQR), events/hour2.5 (1–5.2)16.3 (8.4–25.6)**3.8 (1.3–9.6)7.8 (2.2–17)
Mean SpO2, mean (SD), %94.5 (2.3)93.5 (2)*94.4 (2.3)93.5 (1.8)*
Minimum SpO2, mean (SD), %88.7 (4.4)81.1 (6.7)**87 (6.3)82.8 (5.7)**
CT90, median (IQR), %0 (0–0.6)3 (0.7–13)**0.1 (0–2.9)2.8 (0.2–13)**
Oxygen desaturation index, median (IQR) (≥3%)4.1 (1.5–10.3)37.5 (23.7–55.9)**6.4 (1.8–14.6)39.7 (23.7–62.2)**
  • Values are expressed as mean (SD) or median (IQR) as appropriate.

  • t-Test or Wilcoxon rank-sum test and χ2 analysis or Fisher’s exact test were conducted to examine differences in the characteristics of participants with sleep and central apnoea.

  • *P<0.05, **P<0.001.

  • †Cardiovascular diseases include angina, myocardial infarction, arrhythmia, peripheral vascular disease or stroke.

  • AHI, Apnoea-Hypopnoea Index; CAI, Central Apnoea Index; COPD, chronic obstructive pulmonary disease; CT90, cumulative time SpO2<90%; MME, morphine milligram equivalents; SpO2, oxyhaemoglobin saturation; STOP-Bang, a screening tool for sleep apnoea (Snoring, Tiredness, Observed apnoea, high blood Pressure, Body mass index, age, neck circumference and male gender).