| Summary: | Intermittent UV-exposure is a risk factor for melanoma. Recreational sun-exposure (e.g. holiday) is associated with melanoma incidence. Effective and affordable interventions to promote sun-protection behaviours (SPB) are needed. This PhD thesis describes the development of a behavioural change intervention to promote SPB amongst holidaymakers and a pilot of acceptability, feasibility, and fidelity of the intervention. A systematic review was conducted to appraise efficacy of behavioural interventions to change SPB and experience of sunburn. Twenty-three randomised-controlled trials (RCT) were included and no evidence was found for the efficacy of interventions in reducing tanning, promoting protective clothing and seeking shade. Larger effects were observed for self-reported sun-exposure and number of sunburn experienced. Moderator analyses showed that effective interventions were more likely to stimulate social norms and provide appearance-based information about photoaging. A qualitative study based on the theory domain framework was conducted to investigate perceptions of sun-related experiences and determinants of SPB. In a semi-structured interview, 17 holidaymakers showed a desire to tan attributing a high value to it during holidays. Most respondents knew how to perform SPB and identified key barriers to SPB. Findings from systematic review and qualitative work informed the development and design of an evidence-based intervention. The prototype of the mobile phone based (app) intervention was initially tested using a user-centred design: 17 participants were satisfied with the prototype and expressed willingness to use it, with minor changes being introduced to optimise acceptability. Novel outcome measures to assess sun protection behaviours were also explored. The two newly developed methods of outcome assessment (sunscreen use events classifier and mDNA damage caused by UV exposure) show robust evidence for the assessment of sun protection behaviours and skin damage during holidays. This work contributed to the development of a full protocol for the outcome assessment in a definitive trial. Another systematic review was conducted to synthesize evidence on the question-behaviour effect (QBE) for health-related behaviours. Forty-one studies were included assessing a range of health behaviours. Findings showed a small QBE. Studies showed moderate heterogeneity, variable methodological quality and evidence for publication bias. No dose-response relationship was found. Risk of bias within studies and publication bias indicate that the observed small effect size may be an over-estimate. Based on these findings, no changes would be introduced to the protocol of the definitive trial to tackle QBE. A pilot study assessing the acceptability, feasibility and fidelity of the app use showed that the intervention was feasible and highly acceptable. Findings from the pilot study will inform a definitive RCT.
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