Photoprotection in Outdoor Sports: A Review of the Literature and Recommendations to Reduce Risk Among Athletes

De Castro-Maqueda et al. found that elite water sports athletes were exposed for around 4 h per day [13], and elite kitesurfers for 13.93 h per week [14], of whom only 6.9% avoided peak hours [14]. In runners in Portugal, 19% trained between 10 am and 6 pm [15]; in Brazil, 57% trained before 10 am [16]. Teenage skateboarders (Spain) spent more than 90 days per year and at least 5 h a day outdoors [17]. Collegiate athletes (USA) spent an average 4 h per day and 10 months per year training outdoors [18]. The doses of UV exposure are summarised in Table 1.

In an Australian study of mixed sports (soccer, hockey, surf lifesaving and tennis) in 18- to 30-year-olds, almost half used sunscreen inadequately and almost one third did not use it at all [19]. In another study of mixed sports, 29.5% reported no sunscreen use, and only 20.2% had adequate use (sun protection factor [SPF] at least 30 with reapplication) [20]. Lawler et al. noted respective sports’ rules influenced behaviours [21]. In elite rugby, field hockey, and rowing athletes in New Zealand, although 66% were concerned about skin cancer, only 9% always applied sunscreen before going out in the sun, and one third reported intentionally tanning [22]. In collegiate athletes [18], although almost all (96%) thought that sunscreen helps prevent skin cancer, more than half never used it.

A survey of retired Australian cricketers (mean age, 45 years) [23] found that hats were the most popular method, with 65.9% always wearing one during matches, followed by long-sleeve shirt use (19.5% “always”) and sunscreen use (15% “always”).

Among Austrian marathon runners, most (96.7%) wore shorts and short-sleeved (87.6%) or sleeveless (11.0%) shirts, and just over half (56.2%) used sunscreen regularly [12]. In Portugal, only 23.5% of runners had adequate sun protection behaviour; 17% always used a hat, 12% consistently applied sunscreen before training, and 4% used a long-sleeved shirt [15]. In marathon runners in Spain, sunglasses (66.4%) and sunscreen (58.2%) were the most common practices, with less habitual use of a hat (33.6%) or long-sleeved clothing (10.9%) [24]. A similar pattern was observed in mountain marathon runners in Spain [25]. In Brazil, 86% of runners wore clothing or accessories for sun protection; 62% wore sunscreen, which was usually only applied to the face, and 53% used SPF greater than 30 [16].

The most common practices among Spanish cyclists [26] were use of a hat (95.5%) and sunglasses (92.8%); the least common were long-sleeved shirts and long trousers (6.2%) and seeking shade (23.1%). Only 39.2% applied sunscreen [27].

Skiers and snowboarders [28] had “inconsistent” compliance with recommendations in a study of more than 4000 adults in western North America: only 4.4% complied with all advice [28]. Of those wearing sunscreen, most (73.2%) applied it 30 min before exposure, but only 20.4% reapplied after 2 h [28].

Among surfers, windsurfers and Olympic sailors from 30 countries, aged 16–30 years, sunscreen was the most-used form of photoprotection, yet 22.5% reported never using it, and 31.1% did not reapply after 2 h [13], with some differences in habits among different sports. In the 2019 Para World Sailing Championships, elite sailors with disabilities from 19 countries reported a very low rate (28.6%) of avoidance of midday sun and insufficient sunscreen reapplication (33.9% did not reapply at all and 16.1% reapplied every 1–2 h); use of sunglasses (85.7%), sunscreen (83.9%) and hat (75%) fared better [26]. In handball players, approximately half did not apply sunscreen at all when training or competing [29].

Teenage skateboarders in Spain [17] were found to wear long-sleeved shirts (65.9%); however, only 18.7% used sunscreen while skating, compared with a 33.3% rate in the same group when at the beach. Less than 40% reported habits like staying in the shade, wearing a hat, sunglasses, or avoiding peak hours [17].

In mountain guides [30], 34.4% reported using sunscreen occasionally, rarely, or never. Of those who did use it, around one third wore SPF less than 30. Long-sleeved shirts were worn by 16.1%, long trousers by 43.5%, and hats by 79.0%. A later study in a similar population found that 86% used sunscreen often or always [31].

Even in athletes who were transplant recipients—and therefore immunosuppressed with increased risk of photo-induced skin cancers—31% did not use sunscreen regularly, despite recognising the importance of photoprotection [32].

Reports of sunburn during the previous season range from 19.7% in Brazilian runners [16] up to 84.7% in elite kitesurfers [14]. Among adults in the US general population, increased levels of physical activity have been associated with higher levels of sunburn [33]. Wysong et al. compared sunburn rates in athletes vs the general population of a similar age: while 86% of athletes reported burns in the past year, only between one third and one half of the general population did [18].

Using erythema as a surrogate for skin cancer risk is reasonable, but self-reported erythema will probably be underestimated. Petersen et al. [34] found that researchers detected up to 28% more of objectively measured erythema than subjects did, concluding that erythema was “considerably underestimated”; in skiers, they found agreement between subjects and researchers in just 57% [34]. Another limitation of using sunburn as an indicator of risk is that skin phototypes that do not burn easily are still exposed to dangerous radiation, and that long-term sub-erythemogenic doses can still cause DNA mutation [35]. Furthermore, keratinocyte carcinoma, in particular squamous cell carcinoma (SCC), correlates more with chronic exposure rather than burn episodes [36].

Zink et al. found that around 50–60% of mountain guides [30, 31] had undergone dermatological examination by a medical professional, with significant differences according to age, education, number of tours per month, and knowledge regarding skin cancer screening [31]. De Castro-Maqueda reported 83.3% of elite water sports athletes had not had a medical skin examination, and 87.5% did not self-examine their skin [30]; 87–95% of handball players had not examined their skin over the last year [29]; and 78.8% of kitesurfers had not examined their skin during the previous year, but 54.2% had consulted a dermatologist [37]. Sixty percent of marathon runners in Austria had never had their naevi checked by a dermatologist [38]. Among Spanish cyclists 61.0% did not examine their skin regularly [27].

Several studies have analysed which variables are predictors of sun-safe behaviour in sporting populations. In some, patterns mirror the general population, but others have found no significant differences among population subgroups [13, 22]. The main patterns reported are those of safer behaviour in older, female athletes [4, 6, 15, 28, 39], and those with greater awareness or concern about skin damage or skin cancer, or knowing someone with skin cancer [4, 18, 28]. Lawler et al. found varying degrees of sex differences depending on what was assessed: women were more likely to wear sleeveless tops and short shorts, more likely to wear sunscreen (though not in all sports), but not more likely to reapply it (no difference between sexes) [21]. Single marital status has been associated with higher risk of sunburn [15, 25]. Duarte found that education level affected knowledge of skin cancer but did not affect behaviour [15]. Price et al. and Buller et al. found that those with burn-predisposed skin types were more likely to protect their skin [6, 28].

Behaviour is influenced by demographic, environmental, and psychosocial factors [39], such as skin cancer risk perceptions, perceived barriers to sunscreen use, lower perceived benefits and personal norms [19]. Although we cannot assume that knowledge of sun safety always translates to behaviour, the intention to use sunscreen has been associated with more frequent sunscreen use [40, 41]. But there remain some contradictory behaviours and opinions: in kitesurfers [14], nearly 80% agreed that they worried they “might get skin cancer from the sun” and 70.8% worried about sunburn, yet more than 40% enjoyed sunbathing. Among elite Paralympic sailors, despite 82.1% reporting concern about skin cancer, 42.9% enjoyed sunbathing [26]. Other factors to be taken into account are that individuals may underestimate the seriousness of skin cancer [42] and their likelihood of burning [18], or may not seek attention if they feel healthy and do not have obvious skin lesions [31].

Explicit reasons cited for not using sunscreen included forgetfulness and discomfort [18, 29, 40], greasy feel, burning of eyes, causing acne, being time consuming, inconvenient or messy [18, 40], and hindering performance (e.g. slippery hands) [19]. Clothing can also be restrictive or uncomfortable [43].

Getting a suntan may be seen as reflective of a healthy outdoor active lifestyle [44], which has been reflected in so-called health magazines that use “dark-skinned Caucasian” models [45], and include few articles on skin cancer risk reduction [46]. But such opinions are not constant: in a large USA sample of recreational cyclists [40], participants reported they were not interested in tanning; intentions to use sunscreen and actual use correlated with perceived costs and effectiveness and susceptibility to photoaging.

As part of the American College of Sports Medicine (ACSM) 2018 International Roundtable [2], expert participants looked at a pooled analysis [47] that evaluated 12 cohorts with a total of 12,438 melanoma cases. Overall, a high level of physical activity was associated with a greater risk of melanoma relative to low physical activity (hazard ratio, 1.27; 95% confidence interval [CI], 1.16–1.40) [47]. Eight of the cohorts had hazard ratios of 1.2 or greater (range 1.23–1.90), suggesting “a strong and highly consistent association” [2].

Rosso et al. [48] analysed sun exposure patterns in the aetiology of basal cell carcinoma (BCC) and SCC in a Southern European population. One of their key findings was an increased risk of SCC with increasing exposure beyond a threshold of 70,000 cumulative hours in a lifetime. Beach holidays and water sports were independent risk factors for BCC, although outdoor sports in general were not, and they even noted that outdoor sports seemed to protect against SCC occurrence. For BCC, there was a significant association for water sports with intense exposure (e.g. swimming, surfing, or sailing), but a dose–response relationship was not established. A few years later (1999), a case–control study of risk of BCC and SCC in Switzerland [49] found that sun exposure during recreational activities (outdoor sports) showed a twofold increase in BCC risk, with borderline statistical significance as an independent effect (P = 0.05); sunburn was the highest independent risk factor for BCC (odds ratio [OR] 2.4 for more than three sunburns in a lifetime with a significant linear trend), while SCC risk was related to lifetime cumulative exposure [49].

A study of skin cancer risk factors in a German population found that history of winter sports in childhood had an OR of 1.7 for BCC, indicating possible increased risk. Mountaineering in childhood was actually associated with reduced melanoma risk, compared with BCC or healthy controls [50].

Participation in outdoor sports was identified as a risk factor for melanoma in an Argentinian study (OR = 3.2 for more than 5790 lifetime accumulated hours) [51], while Zanetti found that sun exposure during leisure activities in general showed only slightly above-unit OR for melanoma, which was not significant [36]. A Danish study including 28,000 people followed up over 14 years reported, in the men only, a highly significant (P = 0.001) direct association with NMSC for vigorous activity vs low activity, with a rate ratio of 1.72 (95% CI 1.23–2.40) [52].

Dozier et al. found a significantly higher incidence of BCC in surfers than a control population: 16.3% vs 3.2% [53]. In the surfers (mean age 29.7 years; 90% male), 20/49 (41%) had actinic keratoses (AK), 8 (16%) had BCC, and none had SCC or melanoma; 18 had clinically atypical moles. These rates were higher than the control for BCC (statistically significant), and higher but not statistically significant for AK and atypical moles. Climstein et al. reported on the lifetime prevalence of skin cancer (melanoma, SCC and BCC) in 1348 Australian recreational and competitive surfers [54]: BCC was the most common (6.8%), followed by melanoma (1.4%) then SCC (0.6%). The relative risk of skin cancer was significantly higher in competitive than recreational surfers [54], and years surfing was the most significant risk factor. Noble-Jerks’ survey [23] of retired cricketers did not find a higher rate of skin cancer (any type) than in the general population: 38% of their respondents had been diagnosed with at least one skin cancer [23].

Zink’s study of mountain and ski guides found that 43.5% had a diagnosis of NMSC or a premalignant lesion (mostly AK) [30]. This may be more suitably attributed to the category of occupational exposure, with certain factors beyond the control of the individual. In some countries (e.g. Germany), KC (formerly NMSC) is now recognised as an occupational disease [30].

Skin cancer data are not always available. Often, other variables that represent increased risk of KC and/or melanoma are used, such as exposure dose or number of naevi [36], total exposure dose being more closely associated with SCC, while melanoma are more associated with intense sun exposure during infancy.

Mahé et al. [55] looked at risk of UV-related skin lesions in children. In those who played outdoor sports, the naevus count and acquired naevus count were higher, reaching statistical significance. Richtig et al. studied potential melanoma markers in 150 marathon runners (all white, mean age 39.6 years, mostly phototype II and III) [38]. They assessed lentigines and naevi on the shoulder and buttock, finding statistically significant differences between the two areas for naevi and lentigines; 17.3% had more than 50 naevi and 35.3% had atypical naevi. Number of lentigines correlated with lifetime sunburn history and type of sportswear, and number of naevi correlated with training parameters (heart rate, training velocity, physical strain). Ambros-Rudolph et al. [11] also found that marathon runners had significantly more atypical melanocytic naevi and solar lentigines than their control population [11]. Del Boz et al. found a high prevalence of skin cancer and AK in golf players: about 10.7% and 40%, respectively [56]; by comparison, indoor workers at the same resort had no diagnoses of skin cancer and only 1.7% had AK [56].

Solar radiation is also a key driver of skin aging [57], accelerating the formation of uneven pigmentation, wrinkles, and sagging skin; while not pathological, this could serve as a further motivation for protection.

Exposure dose is affected by geographic location, body position [58] and other individual sport characteristics; multiple studies have measured and/or calculated UV exposure, as summarised in Table 1.

The International Commission on Non-Ionizing Radiation Protection (ICNIRP) and American Conference of Governmental Industrial Hygienists (ACGIH) set an exposure limit for ultraviolet radiation of 0.3 MED per 8 h [59‐61]. At a cycling event in the Australian winter, the mean daily UV exposure, with some variation across body sites, exceeded this limit [59], and the authors suggested these doses would be generalizable to Canadian, Scandinavian and British populations in summer. Tour de Suisse cyclists were exposed to more than 30 times this international exposure limit each day [60].

On the basis of exposure times, Downs et al. [62] calculated the relative risk of developing BCC or SCC for people with a golfing habit compared with other regular office workers, assuming a lifelong regular habit. This was 1.11 (forearm) and 1.16 (upper back) for BCC and 1.15 (forearm) and 1.22 (upper back) for SCC [62].

Exposure doses are further influenced by setting. Rigel et al. noted, in an alpine ski environment, a 2–3% increase in UV irradiance for each 100 m of altitude, and up to a 40% increase due to the albedo (reflectance) of snow [8]. They concluded [63] that skiers with type I and II skin are repeatedly exposed to erythemal and suberythemal levels of UV radiation that can cause photodamage and potentially increase their risk of skin cancer [63]. Downs et al. [64] calculated the exposure for athletes expected to compete at the 2020 Olympics (Tokyo) across 20 outdoor sporting disciplines, taking into account body position, event duration, event schedule, atmospheric parameters, UV surface albedo, and protection by clothing, to determine the likely biologically effective UV dose received [64] (Table 1).