Validation of Questionnaire and Diary Measures of Time Outdoors Against an Objective Measure of Personal Ultraviolet Radiation Exposure

Self-reported sun exposure is commonly measured using questionnaires or diaries, but there are limited data on their validity, particularly for population subgroups. This research aimed to compare self-reported sun exposure, measured as (1) habitual time outdoors over the past month on weekends and weekdays and (2) a 4-day diary measure, against objective measurement of personal ultraviolet radiation using polysulfone film dosimeters. From November 2015 to January 2016, 94 people (22-69 years and living in New South Wales, Australia) completed a questionnaire, 4-day diary and 4-day dosimeter measures of overall, weekday and weekend sun exposure. Spearman correlations and Bland-Altman plots were used to measure agreement. The overall weekly correlation was 0.57 (95% confidence interval [CI] 0.44, 0.68) between standard erythemal doses (SEDs) measured by dosimeter and time spent outdoors measured by questionnaire, 0.74 (95% CI 0.66-0.81) between dosimeter and diary, and 0.59 (95% CI 0.48-0.68) between questionnaire and diary measures. Validity was lower for younger people and weekend sun exposure. There was strong correlation between dosimeter and sun diary measures and moderate correlation between dosimeter and questionnaire measures. Daily measurement over a longer period may be required to accurately capture weeklong sun exposure in all population subgroups.