Measuring behavioral interventions by questionnaires and prospective diaries: an example of sunscreen use

Abstract

Background: Diaries are used to measure behavior in intervention trials, despite the tendency of diaries to overestimate adherence.

Methods: We estimated the frequency of sunscreen application using prospective diaries and a questionnaire in a trial evaluating sunscreen use.

Results: Sunscreen application was reported more frequently in the diaries than in the questionnaire by the intervention group. This was supported by an increase in the weight of sunscreen used during the times participants were keeping diaries.

Conclusions: Diaries may be better as an aid to increase adherence than as a tool for its estimation. Use of diaries did not overestimate the frequency of application in the control group.