Investigating if changing the wording of a study invitation letter increased recruitment in a project promoting tobacco cessation in a town with high smoking rates.

BACKGROUND: Invitation letters can be the first point of contact between research staff and potential participants and a number of modifiable variables have been studied to improve their effectiveness. The aim of this analysis was to determine if lower reading levels and “gain-framed” messages improved recruitment for a RCT that mailed nicotine replacement therapy (NRT) patches for smoking cessation. METHODS: Invitation letters were created which varied in a two-by-two design by reading level and message framing. The letters were randomly mailed to all households in a community selected to receive targeted distribution of NRT patches. RESULTS: There were no significant differences found in the number of participants enrolled. CONCLUSION: Future research investigating factors to improve invitation letters is merited despite current project limitations. TRIAL REGISTRATION: ClinicalTrials.gov NCT04534231.