Subject characteristics
| Variables | Placebo | Heated humidification# |
| Subjects n | 36 | 34 |
| Sex M:F | 34:2 | 28:6 |
| Age yrs | 51.2±2.2 (20–72) | 50.6±1.6 (28–67) |
| BMI kg·m−2 | 33.6±0.9 (25.3–44.6) | 35.2±0.9 (27.2–48.7) |
| ESS¶ | 10.8±1.0 (0–23) | 11.3±0.7 (3–19) |
| AHI events·h−1 | 43.5±4.6 (6.2–111.7) | 44.4±4.1 (2.7–82.8) |
| Nadir Sa,O2 % | 82.4±1.2 (65–93) | 80.6±1.8 (59–97) |
| History of oral-facial surgery % | 17 | 33 |
| History of allergic rhinitis % | 37 | 50 |
| History of nasal stuffiness+ % | ||
| Never | 9 | 10 |
| Occasional | 37 | 37 |
| Frequent | 54 | 53 |
| History of runny nose+ % | ||
| Never | 6 | 21 |
| Occasional | 77 | 72 |
| Frequent | 17 | 7 |
| History of sore throat+ % | ||
| Never | 27 | 17 |
| Occasional | 50 | 55 |
| Frequent | 23 | 28 |
| Nasal steroids use+ % | 46 | 40 |
Data are presented as mean±sem (range), n or the percentage of subjects within the treatment group. M: male; F: female; BMI: body mass index; ESS: Epworth Sleepiness Scale; AHI: apnoea-hypopnoea episodes per hour of sleep; Nadir Sa,O2: lowest oxygen saturation during sleep. #: between group comparisons with unpaired t-test and Chi-squared test (all p-values >0.05); ¶: score ranges from 0–24, where 24 is the worst score attainable; +: symptoms in the last 12 months.