Flowchart of the study. (Through returned unanswered questionnaires with comments, information about smoking status at long-term follow-up was given for one in HIT (who was smokefree) and four in LIT (one was smoke-free). That is the reason for N3=284 while the sum of the lower boxes is 282).
Nohlert et al. BMC Public Health 2013 13:592 doi:10.1186/1471-2458-13-592