Baseline characteristics according to treatment status of 1603 patients with oxygen-dependent fibrotic interstitial lung disease
| BDZs | Opioids | Unexposed | p-value | |
| Subjects | 196 | 252 | 1214 | |
| Age at starting LTOT years | 77.5±8.2 | 76.1±8.9 | 76.3±8.8 | 0.156 |
| Female | 89 (45.4) | 123 (48.8) | 415 (34.2) | <0.001 |
| FEV1 % pred# | 66.3±37.3 | 67.0±39.7 | 71.6±40.3 | 0.106 |
| VC % pred# | 54.7±34.2 | 56.2±35.6 | 60.4±34.7 | 0.052 |
| FEV1/VC# | 0.9±0.3 | 0.9±0.3 | 0.8±0.4 | 0.427 |
| PaO2 breathing air# kPa | 6.5±1.0 | 6.6±1.0 | 6.6±1.0 | 0.441 |
| PaCO2 breathing air# kPa | 5.3±1.0 | 5.3±1.0 | 5.1±0.9 | <0.001 |
| PaO2 breathing oxygen# kPa | 5.7±0.9 | 5.7±1.0 | 5.4±1.0 | 0.001 |
| Smoking status | ||||
| Never-smoker | 61 (31.1) | 66 (26.2) | 338 (27.8) | 0.797 |
| Ex-smoker | 1 (1.0) | 3 (1.2) | 9 (0.7) | |
| Ex-/current smoker | 105 (53.6) | 149 (59.1) | 698 (57.5) | |
| Missing | 30 (15.31) | 37 (14.7) | 178 (14.7) | |
| BMI¶ kg·m−2 | ||||
| <18.5 | 10 (5.1) | 12 (4.8) | 35 (2.9) | 0.579 |
| 18.5–24.9 | 107 (54.6) | 143 (56.8) | 707 (58.2) | |
| 25–29.9 | 53 (27.0) | 67 (26.6) | 314 (25.9) | |
| ≥30 | 26 (13.3) | 30 (11.9) | 158 (13.0) | |
| WHO Performance Status | ||||
| 0–1 | 76 (38.8) | 93 (36.9) | 566 (46.6) | <0.001 |
| 2 | 54 (27.6) | 70 (27.8) | 350 (28.8) | |
| 3–4 | 49 (25.0) | 60 (23.8) | 161 (13.3) | |
| Missing | 17 (8.7) | 29 (11.5) | 137 (11.3) | |
| Hospitalisations within 4 years before baseline | 4 (2–6) | 4 (2–6) | 2 (1–4) | <0.001 |
| Hospitalised days out of the 91 days before baseline | 14 (5.5–24) | 15 (8–27) | 11.5 (4–21) | <0.001 |
| Follow-up time hospitalised (follow-up time/hospitalised days) % | 7.6 (2.3–20.3) | 8.4 (2.6–19.8) | 6.2 (2.1–16.8) | 0.175 |
| Cardiovascular diseases n | ||||
| 0 | 45 (23.0) | 59 (23.4) | 416 (34.3) | <0.001 |
| 1 | 3 (1.5) | 3 (1.2) | 58 (4.8) | |
| 2 | 65 (33.2) | 68 (27.0) | 300 (24.7) | |
| ≥3 | 83 (42.4) | 122 (48.4) | 440 (36.2) | |
| Comorbidity | ||||
| COPD | 50 (25.5) | 67 (26.4) | 234 (19.3) | 0.010 |
| Cancer | 81 (41.3) | 107 (42.5) | 417 (34.4) | 0.016 |
| Depression/anxiety | 43 (21.9) | 33 (13.1) | 37 (3.1) | <0.001 |
| Diabetes mellitus | 44 (22.5) | 73 (29.0) | 219 (18.0) | <0.001 |
| Injury | 33 (16.8) | 54 (21.4) | 154 (12.7) | <0.001 |
| Osteoporosis | 11 (5.6) | 35 (13.9) | 47 (3.9) | <0.001 |
| Renal failure | 18 (9.2) | 25 (9.9) | 65 (5.4) | 0.007 |
| Pulmonary hypertension | 12 (6.1) | 24 (9.5) | 86 (7.1) | 0.315 |
| GORD | 12 (6.1) | 18 (7.1) | 37 (3.1) | 0.003 |
| BDZs | ||||
| High (>15 mg·day−1 oral oxazepam equivalent) | 65 (33.2) | 27 (10.7) | ||
| Low (≤15 mg·day−1 oral oxazepam equivalent) | 131 (66.8) | 32 (12.7) | ||
| Opioids | ||||
| High (>30 mg·day−1 oral morphine equivalent) | 33 (16.8) | 122 (48.4) | ||
| Low (≤30 mg·day−1 oral morphine equivalent) | 27 (13.8) | 130 (51.6) | ||
| Oral corticosteroids | 107 (54.6) | 135 (53.6) | 603 (49.7) | 0.284 |
| Azathioprine | 8 (4.1) | 13 (5.2) | 89 (7.3) | 0.142 |
| N-acetylcysteine | 81 (41.3) | 76 (30.2) | 372 (30.6) | 0.010 |
Data presented as n, mean±sd, n (%) or median (interquartile range), unless otherwise stated. LTOT: long-term oxygen therapy; FEV1: forced expiratory volume in 1 s; VC: vital capacity; PaO2: arterial oxygen tension; PaCO2: arterial carbon dioxide tension; BMI: body mass index; WHO: World Health Organization; COPD: chronic obstructive pulmonary disease; GORD: gastro-oesophageal reflux disease; BDZ: benzodiazepine. Immunosuppressive drugs (including mycophenolate) used by five patients at baseline. #: summary statistics for imputed data applying Rubin's combination rules: FEV1 % pred (42.4% missing), VC % pred (42.7% missing), FEV1 (38.9% missing), VC (39.2% missing), PaO2 breathing air (22.4% missing), PaCO2 breathing air (22.8% missing) and PaO2 breathing oxygen (15.5% missing); ¶: missing BMI (31.1%) imputed into category 18.5–24.9 kg·m−2. p-value calculated using ANOVA, Kruskal–Wallis or Chi-squared test.