Introduction

Exposure to ultraviolet radiation (UV) is the main cause of skin cancer [1,2]. Melanoma is the most life-threatening form of skin cancer, while squamous cell carcinoma and basal cell carcinoma also present a substantial burden to public health [3,4]. In Australia the combined incidence of skin cancer is higher than the incidence of any other type of cancer and causes significant mortality (melanoma: 6.9 per 100,000 in 2016; squamous cell carcinoma and basal cell carcinoma combined: 1.9 per 100,000 in 2002) [5]. Australia’s high ambient UV environment and large population proportion with susceptible skin types account for the high incidence rates [6–8]. Skin cancer is a highly preventable disease, with an estimated 96% of melanoma cases in Oceania, and 75% globally, attributable to UV exposure [7]. To prevent skin cancer and other UV-related diseases, the World Health Organization recommends people protect their skin from the sun when the UV Index is 3 or higher [9].

Australia has implemented one of the most sustained and comprehensive suites of programs for skin cancer prevention [10–13]. Initial efforts were modest, relying on unpaid community service announcements on television and dissemination of brochures to raise awareness of skin cancer [11]. In 1988 the multi-component community-wide prevention program ‘SunSmart’ was established in the state of Victoria [12–14], and similar programs followed soon after in other Australian states [13]. These programs are widely acknowledged as being successful in raising public awareness, and promoting preventive behaviours and environmental change for skin cancer prevention [4,15]. In recent years a decrease in melanoma incidence and mortality among Australians born from about 1958 onward has prompted discussion about whether the extent of behaviour change achieved by these programs is sufficient to have contributed to these reduced melanoma rates [16–19]. In reviewing the evidence for behaviour change, one study labelled the extent of behaviour change as relatively ‘modest’, whilst widespread environmental supports for skin cancer prevention are posited as likely having a larger impact [17]. Certainly, during the past 40 years a large number of environmental supports for skin cancer prevention have been introduced in Australia. These supports include the widespread implementation of policies for hat wearing and shade provision in child care centres [20], primary schools [21], and workplaces [14]; the availability of more effective sunscreens that extend protection time and filter a greater range of UV rays [22]; the inclusion of sun protection items as a tax deductible expense for outdoor workers [23]; the increased availability from the 1980s of long-sleeved sun protective swimwear [24]; a ban on use of solaria in 2014 [25]; the provision of UV forecasts in weather reports [26]; and, in recent years, a comprehensive program of grants for community shade [27]. Indeed, rather than a competing influence, many of these environmental changes are a direct result of the advocacy and awareness raising of skin cancer prevention campaigns and programs [14]. However, environmental change is of little benefit without behaviour change. Sustained public education and environmental support are seen as critical to achieving this [28].

Long-term assessment of the population’s sun protection behaviour in Melbourne, Victoria, has provided some evidence of the impact of the SunSmart program [28–31]. However, in these studies assessment of impact focused on the uptake of individual sun protection behaviours, and found that ‘at best’ less than half the population used any given behaviour on summer weekends, with the exception of covering clothing on the legs [29,31]. The focus of these prior studies on use of specific behaviours during activities outdoors on summer weekends is limiting, and may substantially underestimate the behaviour change for this population.

Five sun protection behaviours (using wide-brimmed hats, sunglasses, sunscreen, and covering clothing and staying under shade while outdoors) are promoted by SunSmart, and since each behaviour offers protection from UV exposure, combined efforts need to be considered. Moreover, one of the most effective methods of reducing UV exposure, namely minimising time spent outside during peak UV hours (i.e., 11 AM to 3 PM DST), has not to date been considered in estimating the prevalence of sun protection behaviour. A more nuanced analysis of behaviour change that addresses these gaps in assessing program impact is warranted, including data from the most recent surveys in the context of long-term patterns of change over time.

Methods

Cancer Council Victoria conducted surveys of Melbourne residents’ sun-related attitudes and behaviour over 3 decades during a total of 14 summers between 1987 and 2017. Respondents were recruited to telephone interviews on a weekly cross-sectional basis over 12 to 13 weeks. Eligible respondents were aged 14 to 69 years and recruited via calls made to a random selection of landline telephones and, since 2013, mobile telephones. Verbal consent to participate in the study was sought from respondents, and from guardians of respondents aged 14 to 15 years, following a brief description of the study. The respondents were informed that ‘Today we’re doing a survey about people’s attitudes towards being out in the sun, and we’d like the opinion of people aged 12 to 69’. If the respondent or guardian did not consent, they were thanked for their time and the telephone call was terminated. Weekly demographic quotas were used to retain the desired sample. The study was approved by Cancer Council Victoria’s Human Research Ethics Committee (HREC 0018).

Results

Respondents surveyed

Table 1 describes the demographic characteristics of respondents pooled across each decade. The distributions by age and sex reflect the distribution of the population of Melbourne residents aged 14 to 69 years in each survey year. Most survey respondents had skin that was highly or moderately sensitive to sunburn. Although the proportion of respondents with less sensitive skin increased slightly in the 2010s, recruitment by skin type was relatively equal across the decades. The increase in respondents attaining higher education across the decades was consistent with changes in the population [45,46].

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Table 1. Demographic characteristics of respondents by decade.

https://doi.org/10.1371/journal.pmed.1002932.t001

Tanning attitudes

Preventive beliefs and attitudes regarding suntans increased among respondents in all decades relative to the baseline (Table 2). In 1987–1988 a minority of respondents reported they did not like to get a suntan (adjusted prevalence [AP] = 43.1%). The prevalence of this aversion to suntanning increased rapidly in the 1990s and peaked in the 2010s with the majority of respondents reporting they did not like to get a suntan (AP = 66.1%; adjusted odds ratio [AOR] = 2.78, 95% CI 2.41 to 3.20, p < 0.001). In contrast, many respondents in 1987–1988 disagreed with the statement ‘A suntanned person is more healthy’ (AP = 82.3%). The prevalence of this health belief increased among respondents in the 1990s (AP = 90.3%; AOR = 2.02, 95% CI 1.70 to 2.41, p < 0.001), but was slightly lower in subsequent decades, albeit remaining above the baseline decade. Social norms also became less supportive of tanning in the 1990s. The prevalence of respondents who disagreed with the statement ‘Most of my friends think a suntan is a good thing’ increased from AP = 35.9% in the 1980s to AP = 63.1% in the 1990s (AOR = 3.43, 95% CI 2.99 to 3.92, p < 0.001). This improvement appeared to weaken in the subsequent decades (2000s: AOR = 2.57, 95% CI 2.24 to 2.96, p < 0.001; 2010s: AOR = 2.52, 95% CI 2.17 to 2.91, p < 0.001).

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Table 2. Changes in tanning attitudes among Melbourne residents by decade, relative to before the SunSmart program.^a

https://doi.org/10.1371/journal.pmed.1002932.t002

UV exposure and sun protection behaviour

Table 3 and Figs 1 and 2 describe the changes in UV exposure, individual and composite sun protection behaviours, and sunburn experience of respondents on summer weekends across the decades. Further details on change in the amount of time spent outdoors, the use of covering clothing, and mean body cover across 3 decades are available in S2 and S3 Tables.

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Fig 1. Adjusted prevalence of sun protection behaviours among Australian adults aged 18–69 years (1987–1988 to 2010s).

Used at least 1 sun protection behaviour (SPB) defined as specifically used sunscreen or wore a hat or stayed mostly in the shade when outdoors during peak ultraviolet radiation hours on summer weekends. Data points represent cross-sectional samples from summers in each decade.

https://doi.org/10.1371/journal.pmed.1002932.g001

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Fig 2. Adjusted prevalence of maximal sun protection and sunburn among Australian adults aged 18–69 years (1987–1988 to 2010s).

Data points represent cross-sectional samples from summers in each decade.

https://doi.org/10.1371/journal.pmed.1002932.g002

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Table 3. Sun exposure and sun protection use among Melbourne residents by decade, relative to before the SunSmart program.

https://doi.org/10.1371/journal.pmed.1002932.t003

Long-term reductions in UV exposure among Melbourne residents were observed. Overall, the majority of respondents spent 15 minutes or more outdoors during peak UV hours on at least 1 day on the weekend (unadjusted prevalence of respondents outdoors on either day: 1987–1988, 75.8%; 1990s, 68.3%; 2000s, 70.1%; 2010s, 68.9%). However, the prevalence of respondents outdoors on the Sunday prior to interview was lower (AP 1987–1988 to 2010s: 55.5% to 41.8%). This latter measure of the odds of respondents being outdoors during peak UV hours was adjusted for weather conditions, and demonstrated a significant decline across the decades relative to 1987–1988 (1990s: AOR = 0.72, 95% CI 0.62 to 0.84, p < 0.001; 2000s: AOR = 0.67, 95% CI 0.58 to 0.79, p < 0.001; 2010s: AOR = 0.57, 95% CI 0.48 to 0.66, p < 0.001). The mean length of time respondents spent outdoors on weekends also decreased (1987–1988: 120 min, SE 2.7; 1990s: 118 min, SE 1.5; 2000s: 111, SE 1.9; 2010s: 101 min, SE 2.0).

In the summer before the SunSmart program commenced, relatively few respondents had used SPF 12+ sunscreen (AP = 11.4%) or worn a hat (AP = 19.7%) on summer weekends. Fig 1 illustrates that the use of these specific behaviours greatly increased in the first decade after the initiation of the SunSmart program. In the subsequent decades there was little change in the prevalence of hat wearing. However, another increase in sunscreen use was observed in the 2010s, reaching a nearly 5-fold increase in the odds of sunscreen use relative to 1987–1988 (AOR = 4.73, 95% CI 3.65 to 6.13, p < 0.001). The highest adjusted prevalence of sunscreen use attained across the decades was 36.3% of respondents outdoors on summer weekends in the 2010s. Shade use was also relatively uncommon in 1987–1988 (AP = 19.3%). Although it increased across the decades, the greatest use observed was in the most recent decade, when less than one-third of respondents stayed mostly in the shade outdoors (AP = 28.2%; AOR = 1.68, 95% CI 1.33 to 2.11, p < 0.001).

A much higher prevalence of sun protection behaviour was evident when assessing respondents’ composite behaviour. Moreover, respondents’ use of clothing, hats, and sunscreen on summer weekends protected on average 72% of the body from UV before SunSmart, which increased to 79% in the 1990s and 2000s and 80% in the 2010s. The adjusted prevalence of use of at least 1 sun protection behaviour increased from 39.3% in 1987–1988 to 65.3% in the 1990s and 68.1% by the 2010s among respondents outdoors in peak UV hours (AOR = 3.46, 95% CI 2.83 to 4.23, p < 0.001). Use of maximal sun protection behaviour on both weekend days, including staying indoors during peak UV hours, also increased, from 27.9% in 1987–1988 to 39.1% in the 2010s (AOR = 1.69, 95% CI 1.42 to 2.00, p < 0.001). Additionally, when considering respondents who stayed in the shade during their activities outdoors in peak UV hours on the weekend, a nearly 2-fold shift in maximal sun protection behaviour was observed in the decades following the launch of SunSmart, with approximately half of respondents well protected from UV on summer weekends during this period (AP: 1987–1988, 38.7%; 1990s, 50.7%; 2000s, 50.0%; 2010s, 53.4%).

Discussion

This study provides evidence of substantial improvements in Melbourne residents’ skin cancer prevention attitudes and behaviour and their experience of sunburn in the decades since SunSmart was implemented. The reported use of sun protection rose rapidly in the 1990s from a low base, suggesting that in the initial years of the program it was relatively easy to shift the early adopters to comply with sun protection messages. In later decades improvement in preventive attitudes and behaviours was more gradual. Compellingly, a reduction in sunburn prevalence corresponding with the increased use of sun protection was also evident.

Relative to past studies for this population, we present a more complete appraisal of the spectrum of sun protection behaviours adopted by the population exposed to SunSmart messages. The approach considering composite behaviours revealed a higher level of sun protection behaviour than previously published for this survey, but this level was consistent with the prevalence of sunscreen use and weekend sunburn when analysing change for individual years from 1987 to 2007 [29]. Our analysis highlights the importance of recognising that reducing exposure to UV involves numerous behaviours that individually or together may provide adequate protection from UV. Additionally, a significant reduction in prevalence and amount of time spent outdoors during peak UV hours across the decades was evident, with the greatest reduction in the most recent decades, which had not previously been observed [29]. This suggests that pooling the survey years into decades in this study was beneficial for detecting the cumulative effects of incremental changes from year to year. The finding that a considerable proportion of respondents are staying indoors during peak UV hours on both weekend days or staying under shade when outside suggests that these behaviours have an important and increasing role in providing adequate levels of UV protection on summer weekends.

Of specific interest is whether or not the findings provide evidence of a sufficient shift in the population’s sun protection behaviour to have contributed to the downturn in melanoma incidence rates among younger cohorts in Australia. Indeed, the timing (with greatest improvement in the 1990s) and the size of the behaviour change (2-fold to 4-fold) observed for the Melbourne population suggests this is feasible. The cross-sectional study design and absence of a control population are limiting for this study. Nonetheless, implementation of a randomised trial to provide evidence of a causal link between SunSmart and the decline in skin cancer rates would be impractical in the context of the population-wide skin cancer prevention programs implemented across Australia [47]. Multiple studies have aimed to bridge this gap in evidence between prevention programs and behavioural outcomes, including by measuring program reach [12], monitoring the growing prevalence of sun protection policies and regulations [12], and analysing the association between the dose of campaign advertising and sun protection behaviour [28,31]. Moreover, the programs implemented are underpinned by a strong theoretical foundation including epidemiological evidence that UV causes skin cancer [1,39,48], evidence of the effectiveness of sun protection measures [49–53], and health promotion and behaviour change principles [12,54].

Although it is possible that secular trends such as changing interest in outdoor activities and increased immigration from populations with low melanoma risk may explain some of the decline in melanoma rates in Australia [17], the large program investment [12] and shift in sun protection behaviours observed in the current study precede the substantial increases in screen time due to the evolution of smart phones and social media in the early 2000s. Furthermore, it is unlikely the more protective sunscreen formulations introduced in the early 2000s would have yet had time to produce a substantial impact on melanoma rates, given an estimated 20-year lag between exposure and development of melanoma [55]. The strong association between the extent of exposure to SunSmart campaign advertising and weekend sun protection behaviour [28,31] suggests that program activities are a significant driver of behaviour change. Moreover, program-driven environmental changes [12], including sun protection policies [56,57] and provision of shade [12], have been shown to be effective in prompting and supporting increased sun protection behaviour.

It appears more likely than not that the operation of the SunSmart skin cancer prevention program over more than 3 decades has reduced the population’s exposure to UV, which may have contributed to a reduced burden of melanoma. It is estimated that every dollar invested in skin cancer prevention programs returns AU$3.20 in reduced burden of the disease [58]. It is therefore important to continue to regularly motivate the population and provide supportive environments to ensure that an adequate level of sun protection is sustained among the population. It is reasonable to expect that, without commitment to environmental change and public-awareness-raising activities by skin cancer prevention programs, a slow decline in sun protection of future cohorts may ensue [59]. The consistency of the survey methods used across the years is a strength of the study given that this minimised bias in analysing changes in prevalence over time. The time- and location-based self-report measures have shown good congruence with observed sun protection behaviour in public outdoor settings over time when assessing long-term behaviour change [35]. Accordingly, any social desirability bias that might otherwise explain change over time in reported behaviour is likely to be relatively small [35]. Congruence with the patterns of change over time nationally also provides further validation of the findings. Specifically, the increase in preventive attitudes regarding tanning and continued increase in use of sunscreen, reduction in time spent outdoors in peak UV hours, and reduced sunburn among Melbourne residents in the 2010s appeared relatively consistent with improvements observed nationally for the period from 2003 to 2011 [60].

There is limited comparability of these time- and location-based measures of recent behaviour with those used by population monitoring studies internationally [61,62]. The composite sun protection measure used in the longest running national sun protection survey in the US is based on the use of sunscreen or covering clothing or seeking shade on a regular basis, namely ‘most of the time’ or ‘always’, when outside for 1 hour or more in summer [63,64]. This composite measure used in the US is similar to the measure presented in the current study for minimal protection, i.e., use of least 1 sun protection behaviour, although the latter is based on sun exposure for a recent day during peak UV hours rather than usual behaviour. The prevalence of use of sunscreen and use of at least 1 sun protection behaviour among US and Australian adults appear to be of similar magnitude, with a somewhat similar pattern of increase during the past 2 decades, albeit with a stronger increase in the 2010s decade in Australia. However, there is no corresponding decrease in sunburn for this period in the US. It is probable that the measure of usual behaviour recalled over a longer time frame and for an extended period of sun exposure (>1 hour) overestimates UV protection. In high-UV environments during summer, a fair-skinned person will experience sunburn in less than 1 hour [65]. In the current study, the pattern of change in the prevalence of maximal sun protection corresponded most closely with the change in sunburn over time, compared with the other sun protection measures, highlighting the effectiveness of using either sun avoidance or multiple sun protection strategies together. This is encouraging given that the maximal sun protection measure is in line with the WHO guidelines for sun protection [9,66], which recommend limiting time in the midday sun and using a combination of sun protection behaviours when outdoors. However, recall of sunburn over an extended period of time (i.e., over the past month or past summer), rather than 2 to 3 days ago, may also explain the limited change in sunburn prevalence observed in the US. Nevertheless, annual surveys of sunburn rates among adults in Denmark, using a measure comparable to that in the US, did detect a small decline in sunburn following an intensive public education campaign [67], so other factors may be involved. It is interesting that the changes to sun protection in the US have occurred with minimal public education on skin cancer prevention. Chang et al. highlight the other socio-cultural influences on sun protection historically, including changes in swimwear fashions, travel, and leisure time in the past century [68].

One limitation of the study is that the measures were focused on behaviour during peak UV hours on summer weekends, although respondents may have had considerable UV exposure at other times. Additionally, in defining maximal sun protection behaviour, we acknowledge that small amounts of UV exposure may occur even when staying indoors or applying sunscreen to all exposed skin when outdoors [22,69]. The self-reported nature of the survey is a further limitation of the measures, but the survey is generally considered reliable [35,70]. We also note a large shift in educational attainment among respondents across the decades. Although this is consistent with the significant increase in school retention and tertiary education in Victoria [71], this and increased exposure to many health campaigns more broadly across the decades may have contributed to improved sun-related attitudes and behaviours [72]. Finally, the findings are limited to the years the survey was conducted, and unmeasured variation within the decades due to non-surveyed years is probable; however, this is unlikely to be substantial given the overall patterns of change observed across the decades. Nonetheless, following 30 years of SunSmart, despite significant behaviour change, the prevalence of use of adequate sun protection behaviours is still less than ideal. Sustained high-reach multi-media campaigns and community programs along with innovative strategies are needed to continue to improve the population’s sun protection behaviour in Australia. Novel strategies adopted recently for skin cancer prevention in Victoria include promoting daily sunscreen use [73] and creating shade in community settings. The state government is continuing to support creation of shade in community settings with a further AU$15.1 million in shade grants planned for 2019 to 2023 [27]. For countries yet to achieve significant behaviour change, we recommend new programs begin with identifying skin cancer as a problem to be addressed by the community and continually reminding the community of this need. Strategies implemented must be of sufficient scale, with well-funded campaigns and programs to ensure widespread and sustained population reach, and with advocacy for policy and legislative changes to create supportive environments for UV protection across varied community settings.

Conclusions

This comprehensive analysis of changes in reported sun protection behaviour among Melbourne residents over a period of 3 decades shows a significant and sustained improvement. The timing and size of the shift in preventive behaviours implies that SunSmart is likely to have contributed to the reduced incidence in melanoma among younger cohorts observed in recent years. Although definitive evidence of the impact of the SunSmart program on skin cancer rates remains elusive, prevention programs should be supported to maintain and further their strategies, given that lifelong protection is beneficial in reducing risk of skin cancer [1].

Supporting information

Acknowledgments

We thank David Hill and colleagues for conceiving and establishing this monitoring study. The authors also thank the Bureau of Meteorology and Australian Radiation and Nuclear Safety Agency for providing the data on weather conditions and UV levels in Melbourne for the dates relevant to this study. We thank the respondents for their voluntary participation in the telephone interviews, and the staff of the market research company for conducting the recruitment and interviewing. We acknowledge the work of our colleagues from the Cancer Council Australia and affiliated state/territory cancer councils’ National Skin Cancer Committee and the National Cancer Control Initiative for championing the study’s ongoing funding as part of the National Sun Protection Survey data collection.