Verbal self-report is the method most often used to assess sunscreen use, but the data may be confounded by recall error and social desirability. Sunscreen swabbing is a non-invasive procedure to objectively assess the presence of sunscreen on the skin. This study examined the agreement between verbal reports of sunscreen use from survey and diary measures and objectively measured sunscreen use.
Participants were 564 parents, children aged 5–10 years, and lifeguards at 16 swimming pools in four regions of the U.S. Participants completed self-reported measures, including baseline and final surveys, as well as a 4-day diary and objective swabbing measures of sunscreen presence on 2 separate days. Data were collected in 2006 and analyzed in 2006–2007.
Levels of sunscreen use were relatively high based on surveys (65.7%); diary data (40.3%); and swabbing measures (59.1%). Agreement between swabbing and diary measures of sunscreen use was fair to good, with κ statistics for children at 0.40, followed by lifeguards at 0.34 and parents at 0.27. Validity coefficients across measures of sunscreen use were higher for lifeguards and parents than for children, and diary measures were higher than surveys. No systematic errors were found across groups or by gender, latitude, study arm, or risk category.
These findings are comparable to those in other validation studies, including studies of the validity of dietary assessments. Self-reported estimates of sunscreen use by diaries or surveys appear to be as good as objective measures.