Table 2.

Effect of ICS on FEV₁ categorised by smoking status

Period	Study	Smoking status	Change in FEV1*		Estimated effect of ICS on FEV1 outcomes*	P value	Estimated effect of smoking on FEV1 outcomes in ICS users*	P value
			ICS	Placebo
Smoking: pack-year history
0–6 months	Pauwels	Subjects with ≤36 pack-year history†	30	−90	120	<0.001	−50	‡
		Subjects with >36 pack-year history†	0	−70	70	0.57
9–36 months	Pauwels	Subjects with ≤36 pack-year history†	−47	−71	24	0.08	22	‡
		Subjects with >36 pack-year history†	−67	−65	-2	0.65
0–30 months	Snoeck-Stroband	Subjects with ≥42 pack years†	−28	−63	35	0.242	−75	0.023
		Subjects with <42 pack years†	18	−92	110	0.037
Smoking: smoking status
0–6 months	Zheng	Never-smoked (n=52)	261	141	120	0.3592	–	–
		Ex-smokers (n=297)	177	6	171	0.0068	51	‡
		Current smokers (n=96)	112	−85	197	0.0022	0.337662338	‡
0–12 months	Bhatt	Smokers (n=7678)	–	–	22	0.038	–	–
		Ex-smokers (n=8807)	–	–	30	0.005	8	‡

*Change in FEV₁ reported. Values are in mL, except for Pauwels (1999) and Snoeck-Stroband (2015) data are expressed as mL/year.

†Number of participants in each study group not reported.

‡P value cannot be calculated from data.

FEV₁, forced expiratory volume in 1 s; ICS, inhaled corticosteroids.