Validation of sun exposure and protection index (SEPI) for estimation of sun habits

Abstract

Background: In both Sweden and Australia high incidence rates of skin cancer have become a major health problem. In prevention and risk communication, it is important to have reliable ways for identifying people with risky sun habits. In this study the validity and reliability of the questionnaire Sun Exposure Protection Index (SEPI), developed to assess individual's sun habits and their propensity to increase sun protection during routine, often brief, clinical encounters, has been evaluated. The aim of our study was to evaluate validity and reliability of the proposed SEPI scoring instrument, in two countries with markedly different ultraviolet radiation environments (Sweden and Australia).

Method: Two subpopulations in Sweden and Australia respectively were asked to fill out the SEPI together with the previously evaluated Readiness to Alter Sun Protective Behaviour questionnaire (RASP-B) and the associated Sun-protective Behaviours Questionnaire. To test reliability, the SEPI was again filled out by the subjects one month later.

Results: Comparison between SEPI and the questions in the Sun-protective Behaviours Questionnaire, analyzed with Spearman's Rho, showed good correlations regarding sun habits. Comparison between SEPI and RASP-B regarding propensity to increase sun protection showed concurrently lower SEPI mean scores for action stage, but no difference between precontemplation and contemplation stages. The SEPI test-retest analysis indicated stability over time. Internal consistency of the SEPI, assessed with Cronbach's alpha estimation showed values marginally lower than the desired >0.70 coefficient value generally recommended, and was somewhat negatively affected by the question on sunscreen use, likely related to the classic "sunscreen paradox". There were some differences in the performance of the SEPI between the Swedish and Australian samples, possibly due to the influence of "available" sunlight and differing attitudes to behaviour and protection "at home" and on vacation.

Conclusions: SEPI appears to be a stable instrument with an overall acceptable validity and reliability, applicable for use in populations exposed to different UVR environments, in order to evaluate individual sun exposure and protection.

Keywords: Questionnaire; Skin cancer; Sun habits; Sun protection; Ultraviolet exposure.