Sun protection education for adolescents: A feasibility study of a wait-list controlled trial of an intervention using objective measurement of sun exposure

Background People increase their risk of melanoma unless they are protected from the harmful effects of sun exposure during childhood and adolescence. We aimed to assess the feasibility of a three-component sun protection intervention- presentation, booklet, and text messages - and trial parameters. Methods This feasibility wait-list controlled trial was conducted in the United Kingdom in 2018. Students aged 13-15 years were eligible. Feasibility outcomes were collected for recruitment rates; data availability rates for objective measurements of melanin and erythema using a Mexameter and self-reported sunburn occurrences, severity and body location, tanning, sun protection behaviours and SSE collected before (baseline) and after the school summer holidays (follow-up); intervention reach, adherence, perceived impact and acceptability. Quantitative data were analysed using descriptive statistics; qualitative data were analysed thematically. Results Five out of eight schools expressing an interest in participating with four allocated to act as intervention and one control. Four parents/carers opted their child out of the study. 487 out of 724 students on the school register consented to the study at baseline (67%). 385 were in intervention group schools. Objective skin measurements were available for 255 (66%) of the intervention group at baseline and 237 (61%) of the group at follow up. Melanin increased; erythema decreased. Complete self-report data were available for 247 (64%) students in the intervention group. The number of students on the school register who attended the presentation and given the booklet was 379 (98%) and gave their mobile phone number was 155 (40%). No intervention component was perceived as more impactful on sun protection behaviours. Adolescents did not see the relevance of sun protection in the UK or for their age group. Conclusions This is the first study to use a Mexameter to measure skin colour in adolescents. Erythema (visible redness) lasts no more than three days and its measurement before and after a six week summer holiday may not yield relevant or meaningful data. A major challenge is that adolescents do not see the relevance of sun protection and SSE.


Abstract
Background People increase their risk of melanoma unless they are protected from the harmful effects of sun exposure during childhood and adolescence. We aimed to assess the feasibility of a three-component sun protection intervention-presentation, booklet, and text messages -and trial parameters. Methods This feasibility wait-list controlled trial was conducted in the United Kingdom in 2018. Students aged 13-15 years were eligible. Feasibility outcomes were collected for recruitment rates; data availability rates for objective measurements of melanin and erythema using a Mexameter and self-reported sunburn occurrences, severity and body location, tanning, sun protection behaviours and SSE collected before (baseline) and after the school summer holidays (follow-up); intervention reach, adherence, perceived impact and acceptability. Quantitative data were analysed using descriptive statistics; qualitative data were analysed thematically. Results Five out of eight schools expressing an interest in participating with four allocated to act as intervention and one control. Four parents/carers opted their child out of the study. 487 out of 724 students on the school register consented to the study at baseline (67%). 385 were in intervention group schools. Objective skin measurements were available for 255 (66%) of the intervention group at baseline and 237 (61%) of the group at follow up. Melanin increased; erythema decreased. Complete self-report data were available for 247 (64%) students in the intervention group. The number of students on the school register who attended the presentation and given the booklet was 379 (98%) and gave their mobile phone number was 155 (40%). No intervention component was perceived as more impactful on sun protection behaviours. Adolescents did not see the relevance of sun protection in the UK or for their age group. Conclusions This is the first study to use a Mexameter to measure skin colour in adolescents. Erythema (visible redness) lasts no more than three days and its measurement before and after a six week summer holiday may not yield relevant or meaningful data. A major challenge is that adolescents do not see the relevance of sun protection and SSE.

Melanoma risk in adolescence
Sun exposure is important for health; it is involved in vitamin D synthesis and may induce feelings of 3 well-being [1]. Sun overexposure is detrimental to health; 86% of melanoma cases in the UK are caused by overexposure to ultraviolet radiation (UVR) [2]. Overexposure leads to both DNA damage and immunosuppression, which mediate carcinogenesis [3]. In the last decade, melanoma incidence rates have increased by 50% in the UK and are projected to rise by 7% between 2014 and 2035, to 32 cases per 100,000 people by 2035 [4]. The estimated cost to the NHS due to skin cancer will amount to over £180 million per annum in 2020 [5]. Evidence from meta-analyses show that melanoma risk is more closely linked with intermittent exposure to high-intensity sunlight than to chronic sunlight exposure [6] and the risk is around 3 times higher in people who have had sunburn once every 2 years, or 10 times in a decade, compared with people who have never had sunburn [7]. Melanoma risk is increased regardless of whether sunburn occurs in childhood or adulthood [6][7][8]. However, adolescence is a key period for increasing melanoma risk. There is a greater propensity for sunburn during adolescence than childhood [9][10][11][12] or adulthood [13]. Several reports indicate that there is a steady decline in sun protection behaviours from childhood to adolescence [14] [15]. UK studies show that 51% of adolescents experience sunburn in the summer [16] and 44% of adolescents do not use sunscreen [17]. Health in adulthood has antecedents in childhood [18][19][20]; for example, behaviours (e.g. sunbathing) and attitudes (e.g. pro-tanning) associated with skin cancer emerge in adolescence and track into adulthood [21,22]. Adolescence therefore provides a critical window of opportunity for the primary prevention of skin cancer caused by sunburn across the life-course.

Sun protection interventions targeting adolescents
Theories inform what cognitions and emotions need to be addressed in behaviour change interventions. The Common-Sense Model of illness representation and self-regulation (CSM) [23] and Health Action Process Approach (HAPA) [24] informed the intervention being tested in this feasibility study. The CSM suggests that an 'illness representation' (e.g., skin cancer), has four dimensions: the cause dimension represents beliefs regarding the factors that are responsible for causing the illness (e.g., sunburn causes skin cancer), the consequence dimension refers to beliefs regarding the impact of an illness on overall quality of life (e.g., I will die if I get skin cancer), illness identity refers to 4 beliefs about the illness label and knowledge about its symptoms (e.g., a mole that changes shape is a sign of skin cancer), the timeline dimension refers to beliefs about the time-scale or course of the illness (e.g., if I detect skin cancer early I will receive treatment and be cured) [ interventions concluded that they generally produce positive effects of sun protection behaviours [35], which suggests that appearance beliefs is another important dimension to address in sun protection interventions. However, it is not known which psychosocial constructs and risk behaviour models have most explanatory power for sun protection behaviours in adolescence.
Education interventions involve imparting knowledge and developing sun protection skills [36]. Some forms of delivery of an education intervention are likely to be more acceptable to the target audience than others and may influence intervention adherence and thereby effectiveness [37]. Smartphone technology is a form of delivery that offers opportunities to deliver sun protection information using text messaging (also called short messaging service (SMS)) because of high levels (83%) of ownership in the target age group [38]. Moreover, this form of delivering sun protection information may represent a practical and cost-effective approach relative to interventions that are delivered inperson. A systematic review of eight studies concluded that the use of SMS and similar electronic technology improves sun protection behaviours [39]. However, only one included study involved adolescents, which was a pilot study with no control group of 113 adolescents (11-14 years) who received 36 text messages [40]. The study reported significant increases in self-reported wearing of sunscreen, hats and sunglasses [40].
A general criticism of evidence reporting the effect of sun protection interventions is reliance on selfreport. People may present a favourable image of themselves on questionnaires, which is called socially desirable responding [41]. As several systematic reviews have highlighted, a major limitation of previous sun protection intervention studies is lack of objective measurement of sun protection behaviour and clinically-related proximal targets such as, sunburn occurrence [39, 42].

Aims
The feasibility study of an educational sun protection intervention reported in this manuscript was designed to address limitations of our previous education intervention study [29]. The previous intervention was delivered in-person and sun protection behaviours were self-reported. Hence, the main purpose of this study was to assess the feasibility and acceptability of a sun protection education intervention with an additional intervention component -Short Messaging System (SMS). A further aim was to evaluate trial parameters such as, recruitment, use of a wait-list controlled trial design, and objective measurement of skin colour (erythema and melanin). The feasibility study was not powered to measure effect; rather, the purpose was to observe changes in potential outcomes of interest, and in particular, if outcomes changed in the intended direction.

Design
We conducted a feasibility study of a wait-list controlled trial, with five schools allocated by the research team to an intervention group and one school to a wait-list control group. The last school to be recruited was allocated to the control group. The study was conducted in the United Kingdom between June and September in 2018.

Study population and recruitment
The criteria for inclusion in the study were males and females aged between 13 and 15 years. Head teachers of 132 schools in 6 local authorities were contacted by email about the study. Schools were followed up by telephone calls if the head teacher expressed interest in participating in the study.
Recruitment stopped once six schools consented to participate.
For each participating school, study information booklets were distributed to all parents/carers of all eligible students on the school roll, including a form that could be returned if the parent/carer did not assent to their child's participation in the study. Contact details for the research team were included in the booklet, allowing parents/carers the opportunity to contact the research team if they wished to discuss the study. Students whose parents did not opt them out of the study were provided with a verbal overview of the study by a researcher, a study information booklet and consent form. For those students who were opted out of the study by parents/carers and those that did not consent to participate, alternative educational opportunities were provided by the school whilst their classmates participated in the study.

Intervention description
The intervention being tested was refinement of our previous intervention [29]; two intervention components were the same (Components 1 and 2) and our previous study shows that these components improve sun safe intentions [29]; the third additional component was novel and had not been previously tested. The intervention was designed in accordance with two theoretical models -CSM and HAPA. The intervention was developed to address social cognitions by changing beliefs about skin cancer, evoke an emotional response to skin cancer, and shift sun protection intentions to actual behaviour by including action and coping planning.
Component 1: Information delivered during a presentation was designed to address key CSM dimensions (cause, consequence, identity, risk perception, controllability) and included information about personal experiences of skin cancer, incidence patterns, risk factors, associations between disease staging and survival, and benefits of skin self-examination (SSE). The presentation also briefly touched on appearance. A skin cancer nurse specialist delivered the 50-minute presentation on one occasion during the school day in a classroom or hall. After playing a 5-minute film 'Dear 16-year-old me' (http://dcmf.ca), the nurse delivered the presentation with the aid of Microsoft PowerPoint slides.
A young adult skin cancer survivor gave a brief 5-minute talk after the nurse-delivered presentation.
The talk was about his personal experience of melanoma diagnosis at 16 years old, impacts on his life and his views on sunscreen use and SSE. The film and the young person's talk aimed to evoke an emotional response to skin cancer.

Component 2:
This intervention component was based on the HAPA and aimed to shift intentions to use sun protection and conduct SSE by making plans to conduct these behaviours. A booklet with instructions to write sun protection and SSE action plans was handed to students at the presentation.
The booklet also included information about sunscreen use and SSE. Adolescents were asked to complete an action plan for regular monthly sunscreen use and an action plan for SSE. The SSE component of the booklet for instance, had three sections: a) information on the importance of planning; b) instructions of what should be included in the plan; c) formulating 'if-then' action plans (e.g., If I am having a shower then I will check my skin) and coping plans (e.g. To make sure I don't forget, I will add the appointment to my calendar and put a reminder post-it on the fridge).

Component 3:
Automated text messages were delivered on two days of the week for seven weeks after the 50-minute presentation. Messages were developed by the study investigators to apply to key theoretical CSM dimensions and address appearance. A total of 14 messages were developed.
These messages were tailored to the target audience following feedback from a focus group of students (n= 13) who attended one of the participating schools. Participants were shown the messages that the study investigators developed and were asked to provide feedback, including how to make the text messages more likely to motivate themselves to protect their skin. Messages that 8 the participants indicated that they did not like were removed from the list or were revised based on specific suggestions. Messages contained information around sun safety behaviours and information about the effects of excessive exposure to the sun (Table 1). Messages were scheduled in the morning on a Monday and Friday.

Reach and adherence
Intervention reach was objectively measured using school attendance records. Reach was defined as the proportion of students on the school register who attended the presentation and given the booklet

Variables and measures
Outcome variables were measured before the school summer holidays in June (baseline) and after the summer holidays in September (follow-up). Student responses were paired between the two timepoints via use of unique identifier after all questionnaires had been anonymised. Objective measures of sunburn and tanning were collected by two researchers in the classroom. A selfcompleted pen and paper questionnaire was completed by students in the classroom. Items for the self-report questionnaire were recommended by an international working group to measure sunburn and sun protection behaviours [43] and/or used in our previous study [29].

Objective measures of skin colour
The feasibility of objectively measuring sunburn and tanning was assessed by measuring skin colour using a Mexameter, giving a "melanin index" calculated from the intensity of the absorbed and the reflected light at 660 and 880 nm and an "erythema index" from 568 and 660 nm [44]. Three readings were made, each taking only a few seconds, on the right or left dorsal forearms (likely to be exposed to UV radiation) and behind the left or right ear (unlikely to be exposed to UV radiation).
Self-reported sunburn, severity and body location Self-reported sunburn was measured using one item: 'For people with white skin, sunburn is red skin that appears a few hours after being out in the sun and then fades after a few days. For people with naturally dark skin, sunburn is less visible but the skin feels hot in the sun and stays hot and is painful afterwards for a few days. During the last summer holidays, how many times did you have a red OR painful sunburn that lasted a day or more? Students had nine options to choose to report how many times they had sunburn from 0 to ³8.
Sunburn severity was measured using one item: 'Which one of the following best describes your worst case of sunburn during the last summer holidays?' Students had seven options to choose how to report severity: 'Skin got hot and stayed hot for a couple of days, Skin went pink or slightly red, Skin went red but not sore, Skin went red and sore, Skin went red, sore and blistered, or I did not get sunburnt during the summer holidays.' Body location was measured using one item: 'Where on the body was your worst case of sunburn during the last summer holidays?' Students had seven options to choose to report where on the body their worst case of sunburn occurred: 'back, chest, leg or foot, arm or hand, shoulder or neck, head or face, or I did not get sunburnt during the summer holidays.'

Self-reported tanning
Three items were used to measure tanning: i) 'Last summer did you get a suntan?' Students had three options: 'yes, no or don't know'; ii) 'How many days did you sunbathe last summer to try to get a suntan? (by sunbathe, we mean that you stayed out in the sun because you wanted your skin to go browner or more golden in colour). Students had four options '0 days, 1 to 5 days, 6 to 10 days, 11 or

Social-demographic characteristics
Socio-demographic questions were included to gather data on age, gender and ethnicity.

Analyses
As this was a feasibility study, the quantitative data were analysed using descriptive statistics.
Baseline measurements were reported as n (%) for categorical data and mean (standard deviation)

Recruitment, participant characteristics and data availability
Initially eight out of 130 schools indicated an interest in participating in the study. Three schools had difficulty in facilitating the study within the timetable. There were four schools allocated to the intervention group and one school allocated to the control group.

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The school registers across all sites indicate 724 students were eligible. No students declined to participate but some were either absent one the days the research was conducted or in a class that was not included in the study and therefore 487 students consented to the study at baseline (67%), of which 385 (79%) were in the intervention group and 102 (21%) in the control group. Four parents/carers opted their child out of the study; no other students were opted out by parents/carers.
The characteristics of the study group are shown in Table 2. On average the intervention group were older than the control group (average age = 14.3 compared to 13.4) and had slightly more male participants. The distribution of ethnic groups was similar in the intervention and control groups, with the majority of the participants from the White ethnic group.
Objective skin measurements were available for 255 (66%) of the intervention group at baseline and 237 (61%) of the group at follow up. In one school, the researchers ran out of time and could not collect measures from all students. Complete self-report data were available for 247 (64%) adolescents in the intervention schools (i.e. we could pair baseline and follow-up for analysis of change in self-report outcome measures). Only complete data is included in the results below. The study flowchart (Figure 1) shows the number of students screened and assessed for eligibility, excluded, allocated to intervention or control group and the number of students in the intervention schools receiving the intervention and assessed at follow up.

Reach and adherence
The number of intervention group students on the school register who attended the presentation about sun protection (component 1) and were given the booklet (component 2) was: 52%, n=110; 72%, n=93; 91%, n=29; 84%, n=147 for each intervention group school, respectively. The number of students on the school register who gave their mobile number to the research team (component 3) 13 when consenting to the study was: 24%, n=51; 16%, n=21; 31%, n=10; 41%, n=73 for each intervention group school respectively.
Using self-report data, in total, 261 (92%) intervention group students listened to the presentation, 186 (68%) read the booklet with action plans, and 109 (39%) received text messages. Just over one quarter of the group (27%) received all three intervention components. Impact Table 3 summarises intervention group students perceived impact of each intervention component for sun protection and SSE. The most popular response in each category was the middle one, recorded by between 30% and 43% of participants. In general, students perceived the intervention impacted their sun protection behaviours more than SSE with no intervention component perceived as more impactful than another.

Acceptability
Focus groups were conducted in 3 intervention schools with 42 students participating across the sites.
The main theme was relevance. Adolescents did not perceive melanoma risk as a major issue for their age group and because of UK weather. A summary of key points is presented for each of the three intervention components: Component 1 (presentation): Most students said during the focus group that listening to the young adult skin cancer survivor talk about his experience of being diagnosed and treated for skin cancer was the best feature of the presentation. Students could recall what he said. They said that they could relate to him because he was a young person. They believed that the message about sun protection was more powerful coming from someone their age. Students questioned the relevance of a sun protection intervention during adolescence because they associated skin cancer with older people and did not perceive sun protection a priority at this stage in their lives. Further, they did not perceive 14 that they were at skin cancer risk because of the UK weather. Students were able to recall key sun protection information delivered during the presentation including using sunscreen and wearing clothing.
Component 2 (action planning): Students said that they did not complete the action plans for sunscreen use or skin self-examination. Some students were unclear about the purpose of doing such detailed action plans for one behaviour. Nonetheless, some students liked receiving the booklet because it had information about sun protection and skin self examination that they could refer to at a later date should they wish to do so. Component 3 (text messages): Students said that text messages acted as a regular reminder to use sun protection. Students preferred texts with specific advice about how to be safe in the sun and ways of obtaining a tan without sunbathing as opposed to just information about the dangers of UV radiation. Text messages that would make them laugh were welcomed. Students recommended visual examples to accompany text and recommended sending texts when relevant e.g., on sunny days. Some students questioned the relevance of sun protection messages in the UK because of the weather and perceived them as only relevant when they were in countries with regular sunshine.

Melanin and erythema
The change in the melanin and erythema indices across the intervention period are summarised in Table 4 for the intervention group. A positive difference indicates an increase in the index. Indices of melanin increased on both the arm and the ear, with higher increases on the ear. Indices of erythema decreased on both sites. Table 5 shows the numbers of self-reported occurrences of sunburn before and after the intervention.

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The numbers before the intervention refer to the number of occurrences in the previous summer and the numbers after the intervention refer to the number of occurrences during the intervention period.
Due to small numbers, those reporting 4, 5, 6, 7 or 8 or more occurrences have been grouped together as 4 or more occurrences.
Overall, 37% of participants reported the same number of sunburns pre-and post-intervention, 26% reported an increased number of sunburns and 37% reported a decreased number of sunburns.
The extent of the self-reported worst case of sunburn is shown in Table 6. Only those who reported occurrence of sunburn in the previous question are included. The percentage of participants reporting more severe sunburn is significantly lower post-intervention than pre-intervention.
Typically, sunburn was experienced on the shoulder and neck (around 52% of participants) followed by the back (18%) both pre-and post-intervention.

Tanning
Overall, 62% of intervention group participants reported getting a suntan in the summer prior to the intervention and 66% reported a suntan in the summer of the intervention. Table 7 shows the selfreported numbers of days of sunbathing each summer to try to get a suntan.
Just over 50% of participants reported similar sun-tanning behaviour pre-and post-intervention, 23% increased the number of days of sunbathing and 25% decreased the number of days sunbathing.
Very few participants reported using a sun-tanning bed -5 participants reported doing so preintervention, and 4 participants reported doing so post-intervention. None of the participants reported using a sun-tanning bed both pre-and post-intervention. Table 8 shows the self-reported use of sun protection measures pre-and post-intervention. The table shows the number and percentage of participants who reported taking each sun protection measure either sometimes or often. There was little change in behaviours across the intervention period.

Skin self-examination
Only 7 (3%) of participants reported examining their skin for signs of possible skin cancer on a regular basis pre-intervention, rising to 26 (11%) of participants post-intervention.

Discussion
We successfully recruited and retained five schools and allocated one school to a wait-list control group. Hence, this small feasibility study suggests that the use of a wait-list controlled study design is acceptable. In this feasibility study, head teachers were approached only once about the study by email; nevertheless, the poor initial response rate highlights that future research conducted in UK secondary schools may face recruitment challenges. The challenges of recruitment and data collection in schools are recognised internationally [46, 47] and therefore we believe that the low response rate in our feasibility study is likely related to the general practicalities of accommodating research in schools irrespective of country. Some head teachers indicated that they were not in a position to participate because there was no space left on the school timetable to accommodate the research. This feasibility study therefore suggests that research teams may have more success in recruiting schools if head teachers are approached prior to the finalisation of timetables, which are often set a year in advance. Other studies recommend approaching a relevant teacher (e.g. a teacher responsible for personal, social and health education) rather than the head teacher [47] and avoiding examination periods when students are either in exams or studying for exams [29].
To our knowledge, this is the first study to use a Mexameter to measure skin colour in adolescents.
The feasibility study shows that objective measurement of melanin and erythema by Mexameter before and after the school summer holiday is acceptable to adolescents and is feasible to collect in schools. Nonetheless, the procedure, while taking only a minute per student, does require planning so that all students in the study can have measures taken within the available time set for the research on the school timetable. The school summer holiday in the UK is when sun exposure is most likely to produce a change in melanin. The direction of change in indices of melanin was as expected, with mean melanin scores increasing over the school summer holidays. Indices of erythema scores decreased. Erythema is the initial inflammatory response in the skin and represents redness of haemoglobin [44]. Hence, erythema (visible redness) is more transitory lasting no more than three days. The study suggests that measuring change in erythema before and after a six week summer holiday may not yield relevant or meaningful data. Instead, future studies should consider measuring erythema immediately before and no more than two days after adolescents have been exposed to the sun and ideally measured on a sunny day when sun protection is recommended. This presents particular challenges in countries such as the UK because sunny days are not guaranteed.
Another purpose of the feasibility study was to evaluate intervention reach and adherence. Reach and adherence can impact on statistical power and interpretation of trial results, including underestimating any efficacy. There is no consensus on the acceptable minimum adherence level in trials and no standardised approach to adherence measurement in the field of complex interventions [48].
A review of treatment adherence in public health research reported that only 27% of research checked adherence to protocol [49] and few prior sun protection intervention studies have assessed reach and adherence. In this feasibility study, intervention reach (i.e., the proportion of students on the school register who attended the presentation) varied considerably between schools. Low reach was primarily due to school-level factors, such as not releasing all classes of eligible students to attend the presentation. Self-reported intervention adherence varied for each of the three intervention components. Adherence to the presentation (92%) and the booklet (68%) is higher in comparison to a study that reported that less than half of online skin cancer risk-reduction modules were completed by young people (18-25 years) [50]. The study found that the intervention was more effective in young people who completed more of the modules, thus highlighting the importance of adherence [51]. In our study, thirty-nine percent of consenting students received SMS (component 3) and only 27% of consenting students received all three intervention components. Given the high level of ownership of a mobile phone in this age group [38] we expected adherence for this component of the intervention to be higher.
The feasibility study provides some insight for participant-level influences on poor adherence. Some students during focus groups for instance, perceived that sun protection text messages were irrelevant for those living in the UK because of the inclement weather and this may account for why some students did not proffer their mobile number. Indeed, a key finding from the focus groups is that adolescents did not perceive that a sun protection intervention was relevant for their age group or people living in the UK because of their perception of the weather. Lack of perceived relevance may explain why the majority of adolescences in the study were neutral in their response to whether the intervention influenced their sun protection behaviours and SSE. Adolescents tend to be less concerned with the distant future [52] when skin cancer is more likely to occur and do not perceive themselves to be at risk of getting skin cancer [40]. A recent qualitative study concluded that lack of knowledge about the long-term risks of sun exposure most likely contributed to the perception that susceptibility to, and severity of the risks of sun exposure is low in adolescents [53]. Hence, lack of perceived relevance is a key challenge for sun protection interventions, particularly in countries with similar weather to the UK.
One of the ways of assessing the feasibility of outcome measures is to describe the direction of change in outcomes from baseline to follow up. As already discussed above, indices of melanin increased in the direction as expected but erythema did not. Severity of the worse case of sunburn decreased. Sun protection behaviour did not change and results on tanning behaviour were mixed.
These mixed results are typical of the few sun protection education intervention studies that have been conducted with adolescents [32, [54][55][56][57][58][59]. For example, a study that used self-report to measure sun protection behaviours and intentions pre-and post-the delivery of 36 SMS over 12 weeks found significant changes in some behaviours/intentions e.g., use of sunscreen but not others e.g., seeking shade and intentional tanning [40]. A randomized controlled trial of an education intervention comprising three class-based sessions found that self-reported weekend sun protection behaviours improved but not weekday sun protection behaviours [60].
Studies that have examined mediator variables point to possible reasons why studies report mixed results and suggest that key risk behaviour theoretical constructs, such as setting goals and action planning for sun protection mediate intervention effects [29,51]. Nonetheless, it is not possible from the current body of evidence of education interventions targeting adolescents to draw any firm conclusions about the effectiveness of sun protection interventions targeting adolescents. This is in part due to methodological limitations; hence, the conclusion drawn over a decade ago in 2004 from a systematic review of evidence of interventions to prevent skin cancer by reducing exposure to UVR remains fast; that is, evidence is insufficient to determine the effectiveness of interventions in secondary schools to reduce sunburn occurrence and severity and change sun protection behaviour [54].

Strengths and limitations
This feasibility study provides new evidence regarding sun protection education interventions that was previously lacking internationally. In particular, it shows that objective measurement of melanin is feasible in schools and acceptable to adolescents. However, several limitations of the study must be noted. First, by definition this feasibility study was not powered to measure intervention effects on sunburn and sun protection behaviours. Second, the recruitment strategy was not designed to yield a representative sample that consisted of a small number of mainly white adolescents and so may not generalise to populations with darker skin pigmentations. Third, the study was conducted in a country with inclement weather. Whether the findings would be similar in countries with different weather conditions in particular, those with hot and sunny climates, is unclear. Finally, given that one of the main findings of this feasibility study was adolescents' perception that sun protection was irrelevant 20 for their age group, the extent to which education interventions alone can reduce sunburn occurrence and sun protection behaviours is questionable.

Conclusions
It is feasible to conduct a wait-list controlled trial of a sun protection education intervention and objectively measure melanin and measure self-reported sun protection behaviours and SSE in adolescents before and after the school summer holiday. A major challenge for sun protection intervention studies is that adolescents do not see the relevance of sun protection and SSE for their age group. Lack of perceived relevance may be compounded in countries with inclement weather.     Table 5: Self-reported occurrence of sunburn pre-and post-intervention