TABLE 1

Study characteristics of the included randomised controlled trials

First author [ref.]	Age group	Duration years	Asthma definition	Asthma severity	ICS intervention	Sample size	Mean age years	Female %	Pre-BD FEV₁
									L	% pred
Beasley [17]	Adults	1	Physician-diagnosed asthma; treatment with SABA only last 3 months	Mild	Budesonide 200 µg twice daily^#	225	34.9	57		90.3
Beasley [17]	Adults	1		Mild	No placebo (open-label)	223	35.8	51		89.2
Becker [18]	Children	1	Physician-diagnosed asthma; ≥6 months of symptoms, FEV₁ >75% pred	Mild	Beclomethasone 200µg twice daily^¶	119	7.6	32.8	1.39	91.3
Becker [18]	Children	1		Mild	Placebo, twice daily	121	7.7	34.7	1.42	92.0
Boulet [19]	Adults	1	Physician-diagnosed asthma; BHR and FEV₁ >70% pred	Mild	Fluticasone 100–250µg daily^#	35	27	54.2	3.55	97.2
Boulet [19]	Adults	1	Physician-diagnosed asthma; BHR and FEV₁ >70% pred	Mild	Placebo daily	34	26	69.7	3.33	98.5
den Otter [20]	Adults	2	Symptoms typical of asthma; BHR or BDR; FEV₁ decline ≥80 mL·year⁻¹	No restriction	Fluticasone 250 µg daily^#	23
den Otter [20]	Adults	2		No restriction	Placebo daily	22
Jonasson [21]	Children	2.3	Physician-diagnosed asthma; ≥1 exacerbation in last 12 months or ≥3 exacerbations ever	Mild	Budesonide 200 µg daily^#	32	10.0	46.9	2.23	102.1
Jonasson [21]	Children	2.3		Mild	Placebo daily	34	9.4	35.3	2.04	104.6
Juniper [22]	Adults	1	Physician-diagnosed asthma; BHR and FEV₁ >70% pred	No restriction	Budesonide 200 µg twice daily^#	16	42.4	62.5		89.9
Juniper [22]	Adults	1	Physician-diagnosed asthma; BHR and FEV₁ >70% pred	No restriction	Placebo twice daily	16	35.1	56.3		92.1
Merkus [23]	Children	2–3	Physician-diagnosed asthma; BHR and FEV₁ 55–90% pred or FEV₁/FVC 50–75% pred	Moderate-severe	Budesonide 100 µg three times daily^¶	34	11.4	62.9		72.2
Merkus [23]	Children	2–3		Moderate-severe	Placebo three times daily	20	10.9	76.7		73.5
O'Byrne [24]	Mostly adults	1	Physician-diagnosed asthma; BHR	Mild	Budesonide 200 µg twice daily^#	1282	39.0	62.2		84.2
O'Byrne [24]	Mostly adults	1	Physician-diagnosed asthma; BHR	Mild	Placebo, twice daily	1277	40.0	60.4		84.1
Osterman [25]	Adults	1	Physician-diagnosed asthma diagnosed within the last year; BHR	No restriction	Budesonide 200 µg twice daily^#	38	33.0	57.9	3.31	93.1
Osterman [25]	Adults	1		No restriction	Placebo twice daily	37	35.0	54.1	3.23	88.7
Pauwels [3]	Adults and children	3	Physician-diagnosed asthma; recent onset ≤2 years; variable airflow limitation	Mild	Budesonide 200–400 µg daily^#	3597	24.0	54.2		86.3
Pauwels [3]	Adults and children	3		Mild	Placebo daily	3568	24.0	54.0		86.6
Simons [26]	Children	1	Physician-diagnosed asthma; BHR and BDR and FEV₁>70% pred	Mild	Beclomethasone 200 µg twice daily^¶	81	9.6	41.0	1.89	92.0
Simons [26]	Children	1	Physician-diagnosed asthma; BHR and BDR and FEV₁>70% pred	Mild	Placebo twice daily	80	9.5	45.0	1.88	96.0
Tonascia [27]	Children	4.3	Physician-diagnosed asthma; BHR	Mild-moderate	Budesonide 200 µg twice daily^¶	311	9.0	41.8		93.6
Tonascia [27]	Children	4.3	Physician-diagnosed asthma; BHR	Mild-moderate	Placebo, twice daily	418	9.0	44.0		94.2
Ward [12]	Adults	1	Physician-diagnosed asthma; positive skin prick testing to ≥3 common aeroallergens	Mild-moderate	Fluticasone 750 µg twice daily⁺	17				96.0
Ward [12]	Adults	1		Mild-moderate	Placebo twice daily	18				94.0

ICS: inhaled corticosteroid; BD: bronchodilator; FEV₁: forced expiratory volume in 1 s; SABA: short-acting β₂-agonist; BHR: bronchial hyperresponsiveness; BDR: bronchodilator reversibility; FVC: forced vital capacity. ^#: low-dose ICS; ^¶: medium-dose ICS; ⁺: high-dose ICS.