Blondal 1999.

Study characteristics
Methods	Study design: parallel RCT Country: Iceland Recruitment: community volunteers
Participants	237 smokers (≥ 1 cigarettes per day) 33% men, average age 41 to 43, average tobacco use 25 g/day
Interventions	1) Nicotine nasal spray (NNS) (0.5 mg/dose) plus 15 mg nicotine patches for 3 months, weaning over further 2 months. NNS could be continued for 1 year 2. Placebo nasal spray plus 15 mg nicotine patches on same schedule
Outcomes	Sustained abstinence at 12 months (6‐year data also reported) Validation: CO < 10 ppm Adverse events: measured within 3 months of follow‐up (still using NRT)
Notes	6‐year abstinence 19/118 versus 10/119, OR 2.1 Pharmacia and Upjohn provided the drugs and placebo for this study and measured the cotinine concentrations. Conflicts of interest: TB was a consultant for Pharmacia and Upjohn, and GG and AW are employed by Pharmacia and Upjohn
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "computer generated randomisation code at a local pharmacy"
Allocation concealment (selection bias)	Low risk	Quote: "Pharmacy staff were blinded to the content of the bottles"
Blinding (performance bias and detection bias) All outcomes	Low risk	Clinic staff, pharmacy staff and participants were all blinded to assignment. Codes not broken until after data entry and analyses completed
Incomplete outcome data (attrition bias) All outcomes	Low risk	All participants followed up for at least 12 months