Chen 2014.

Methods	Design Randomised controlled trial Setting Outpatients
Participants	Inclusion criteria Smokers with COPD according to the GOLD criteria, who were > 18 years old. Exclusion criteria People with experience of smoking cessation medication and those with a history of asthma, asbestosis, silicosis, bronchiectasis, or lung cancer. Number randomised Total 85, COPD intervention group (COPD) 42, control group (C) 43 Number followed up Total 80 Age mean (SD): COPD 61.4 (8.6), C 61.6 (7.7) Sex n (%) male: COPD 41 (98), C 41 (95) Cigarettes/day mean (SD): COPD 17.5 (8.4), C 17.2 (9.6) FTND mean (SD): COPD 4.0 (2.0), C 4.1 (2.5) Severity COPD (FEV1/FVC not reported) FEV1% predicted: 11% mild ≥ 80% predicted, 46% moderate ≥ 50% to 80% predicted, 33% severe 30% to 50% predicted, 10% very severe < 30% predicted
Interventions	Behavioural treatment A. COPD intervention Individual cognitive counselling (face‐to‐face) at baseline (20 minutes) by doctors with experience in professional smoking cessation treatment, self help materials, and 9 telephone follow‐ups (weeks 1, 2, 3, 4, 6, 8 and month 3, 4, and 5; > 10 minutes per call). Individual counselling was based on the five A’s principle. The content focused on the correlation between smoking and COPD. B. Control group Simple smoking cessation advice Pharmacological treatment None
Outcomes	Abstinence Prolonged abstinence from week 4 to month 6 of the intervention Validation Exhaled CO < 10 ppm at week 4 and month 6
Notes	Funding Grants from the Chinese National Natural Science Foundation and the Chronic Respiratory Diseases Research Fund of the Chinese Medical Association Conflicts of interest Not reported Correspondence Additional information received after correspondence
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Smokers in each category were assigned to the intervention or control group according to the randomised digital table..."
Allocation concealment (selection bias)	Low risk	A randomised digital table; central allocation
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not possible to blind for behavioural treatment
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	"The carbon monoxide levels were accessed by researchers, they were blinded for the participants', no information on blinding for the doctors who provided the counselling." (Additional information from author)
Incomplete outcome data (attrition bias) All outcomes	Low risk	Low number of missing values and no differential attrition. (Additional information from author)
Selective reporting (reporting bias)	Low risk	All prespecified outcomes were reported
Other bias	Unclear risk	Participants' and personnel's adherence to the intervention protocol was not described