Description of each cohort
| Under 5s | 5 to 17s | 18 to 54s | 55+ | |||||
| N | % | N | % | N | % | N | % | |
| Total | 17 320 | 82 707 | 210 724 | 113 575 | ||||
| F/U median (IQR, years) | 1 (0.5–1.8) | 3.3 (1.4–5.8) | 4.0 (1.7–6.9) | 5.1 (2.4–7.6) | ||||
| Gender | ||||||||
| Female | 6635 | 38.3 | 35 993 | 43.5 | 120 910 | 57.4 | 67 865 | 59.8 |
| Age category* | ||||||||
| 1 | 943 | 5.4 | 13 687 | 16.6 | 37 322 | 17.7 | 46 232 | 40.7 |
| 2 | 3738 | 21.6 | 19 370 | 23.4 | 59 239 | 28.1 | 37 226 | 32.8 |
| 3 | 5606 | 32.4 | 27 619 | 33.4 | 62 750 | 29.8 | 23 460 | 20.7 |
| 4 | 7033 | 40.6 | 22 031 | 26.6 | 51 413 | 24.4 | 6657 | 5.9 |
| IMD† | ||||||||
| 1 | 3472 | 20.1 | 17 987 | 21.8 | 45 058 | 21.4 | 24 310 | 21.4 |
| 2 | 3367 | 19.4 | 17 044 | 20.6 | 45 241 | 21.5 | 27 151 | 23.9 |
| 3 | 3102 | 17.9 | 15 585 | 18.8 | 41 377 | 19.6 | 23 458 | 20.7 |
| 4 | 3772 | 21.8 | 16 765 | 20.3 | 42 673 | 20.3 | 21 356 | 18.8 |
| 5 | 3552 | 20.5 | 15 283 | 18.5 | 36 212 | 17.2 | 17 220 | 15.2 |
| Missing | 55 | 0.3 | 43 | 0.1 | 163 | 0.1 | 80 | 0.1 |
| Smoking | ||||||||
| Never | NA | NA | 61 506 | 74.4 | 102 684 | 48.7 | 42 815 | 37.7 |
| Current | NA | NA | 3476 | 4.2 | 54 669 | 25.9 | 14 826 | 13.1 |
| Ex | NA | NA | 1151 | 1.4 | 53 052 | 25.2 | 55 903 | 49.2 |
| Missing | NA | NA | 16 574 | 20.0 | 319 | 0.2 | 31 | 0.0 |
| BMI | ||||||||
| Normal | 7980 | 46.1 | 23 068 | 27.9 | 69 020 | 32.8 | 29 495 | 26.0 |
| Overweight | 1018 | 5.9 | 6393 | 7.7 | 58 786 | 27.9 | 39 274 | 34.6 |
| Obese | 638 | 3.7 | 4105 | 5.0 | 54 702 | 26.0 | 36 189 | 31.9 |
| Underweight | 683 | 3.9 | 24 589 | 29.7 | 3879 | 1.8 | 2212 | 2.0 |
| Missing | 7001 | 40.4 | 24 552 | 29.7 | 24 337 | 11.6 | 6405 | 5.6 |
| BTS steps | ||||||||
| 1 | 4889 | 28.2 | 33 109 | 40.0 | 86 360 | 41.0 | 24 980 | 22.0 |
| 2 | 6856 | 39.6 | 26 766 | 32.4 | 54 773 | 26.0 | 24 542 | 21.6 |
| 3 | 979 | 5.7 | 3785 | 4.6 | 18 661 | 8.9 | 12 321 | 10.9 |
| 4 | 2227 | 12.9 | 11 782 | 14.3 | 32 821 | 15.6 | 25 714 | 22.6 |
| 5 | 97 | 0.6 | 1148 | 1.4 | 14 663 | 7.0 | 19 425 | 17.1 |
| 6 | <5 | 0.0 | 22 | 0.0 | 623 | 0.3 | 1629 | 1.4 |
| Non-BTS | 480 | 2.8 | 2020 | 2.4 | 2547 | 1.2 | 4613 | 4.1 |
| Missing | 1790 | 10.3 | 4075 | 4.9 | 276 | 0.1 | 351 | 0.3 |
| Atopy | ||||||||
| Yes | 4883 | 28.2 | 25 714 | 31.1 | 54 205 | 25.7 | 25 629 | 22.6 |
| Rhinitis | ||||||||
| Yes | 629 | 3.6 | 6948 | 8.4 | 23 740 | 11.3 | 14 366 | 12.7 |
| GORD | ||||||||
| Yes | 764 | 4.4 | 1854 | 2.2 | 17 150 | 8.1 | 19 755 | 17.4 |
| Anxiety | ||||||||
| Yes | 290 | 1.7 | 4260 | 5.2 | 32 844 | 15.6 | 19 610 | 17.3 |
| Depression | ||||||||
| Yes | NA | NA | 2238 | 2.7 | 45 489 | 21.6 | 23 397 | 20.6 |
| COPD | ||||||||
| Yes | NA | NA | NA | NA | 5756 | 2.7 | 25 781 | 22.7 |
*Age categories are for ‘Under 5s’: 1 (1–1.9 years), 2 (2–2.9 years), 3 (3–3.9 years), 4 (4–4.9 years); ‘5 to 17s’: 1 (5–7 years), 2 (8–10 years), 3 (11–13 years), 4 (14–17 years); ‘18 to 54s’: 1 (18–24 years), 2 (25–34 years), 3 (35–44 years), 4 (45–54 years); ‘55+’: 1 (55–64 years), 2 (65–74 years), 3 (75–84 years), 4 (≥85 years).
†Socioeconomic deprivation scale, 1 is least deprived. BTS steps are defined as 1=no regular preventer, 2=lowest ICS dose appropriate for age (or LTRA alone if <5 years), 3=add LABA (add LTRA if <5 years), 4=increase ICS dose to next level (medium in adults, low dose in children), may add in other therapy (adults: LTRA, theophylline, LAMA; children: LTRA), 5=increase ICS dose (high in adults, medium in children), add fourth drug (adults: LTRA, theophylline, beta agonist tablet, LAMA; children: theophylline), 6=same ICS dose and continuous or frequent use of oral steroids. Children are patients aged below 12 years.
BMI, body mass index; BTS, British Thoracic Society; F/U, follow-up; GORD, gastro-oesophageal reflux disease; ICS, inhaled corticosteroid; LABA, long acting beta-2 agonist; LAMA, long acting muscarinic antagonist; LTRA, leukotriene receptor antagonist; NA, not applicable.