Compliance and data reliability in sun exposure studies with diaries and personal, electronic UV dosimeters

Background/purpose: Skin cancer risk estimations are based on sun exposure data. However, the reliability of collected data in personal ultraviolet (UV) dosimeters studies has not previously been validated. We aimed at investigating the data reliability and subject compliance in a study of sun exposure behaviour among 407 subjects (age range, 4-68 years) during 54 943 days based on time-stamped personal UV dosimeter readings and diary records. Methods: By comparing diary records and UV dosimeter readings on a daily basis, we investigated subject compliance, total sun exposure record, reasons for non-responding along with rates of diary completing errors. Efforts to improve compliance were described. Results: The subject compliance rate was median 93.5% (percent days where the diary was completed and the UV dosimeter was worn). The total sun exposure record rate was median 84.1% (percent of participation days with both UV dosimeter and diary records and where the UV dosimeter was worn). Children, adolescents and golfers had lower sun exposure record rates than the rest of the groups (P < 0.05). No significant difference was found between males and females (P=0.15). The 17 non-responders were 10 children, three adolescents, one sun worshipper, two golfers and one gardener. Correctable diary completing mistakes were found in 3.1% of the days. Children made more completing mistakes than adults (P=0.001). The average estimated error rate was 3.3% and was higher for children (6.3%) and adolescents (3.6%) than the adult groups (2.4%). Conclusion: High subject compliance rate and data reliability were obtained because the investigators were service minded but persistent, offering dosimeter maintenance service within 24 h and scrutinized data for errors and mistakes.