Ultraviolet (UV) radiation has various effects on health. Some are positive, such as the production of vitamin D3, essential for bone mineralization.1 A protective effect, mediated by vitamin D3, has also been suggested against multiple sclerosis2 and the development of prostate cancer,3 although the evidence is still not conclusive.4 Other effects are negative, acting as a risk factor for skin cancer, immunosuppression and cataracts.5

Malignant skin tumours, basal cell carcinoma and spinocellular carcinoma as well as melanoma, are a growing problem in Spain due to their steady increase in recent decades. Annual increases in mortality of 2% have been recorded for melanoma, and the incidence of this neoplasm ranges between 4 to 9/100,000 for men and 3 to 10/100,000 for women.6 Despite this increase, similar to that seen in other countries in southern Europe like Portugal and Greece, the mortality rate from melanoma in Spain is still one of the lowest in Europe, probably because of the characteristics of the cutaneous pigmentation of the population. Nevertheless, the increase in this disease could reflect changes in the sun exposure habits of the Spanish population.6

There is strong evidence that solar radiation is the main environmental risk factor for the three main types of skin cancer,7 with the effect increasing as the intensity of exposure rises.7 There are variations in the relationship between the types of cancer and their localization regarding the time and type of sun exposure,8 but this association is seen even for short-term intermittent exposures and basal cell carcinoma or melanoma.9 Scientific evidence also supports the relationship between exposure to artificial sources of UV radiation and certain types of skin cancer, increasing the risk of melanoma, squamous cell carcinoma10 and basal cell carcinoma.11

In the summer, UV radiation in the Madrid region reaches very high values on the UV index,12 but until now there have been no studies describing the patterns of exposure and its distribution among the population of this region. The estimation of these parameters, using information from self-reported questionnaires, would be very useful for the more efficient planning of skin cancer prevention interventions within the framework of the Regional Plan for the Prevention and Control of Cancer, and could serve as a reference for other countries in southern Europe with high levels of insolation.

The response rate (completed interviews as a percentage of the total sum of completed, partially completed and incompleted/refused interviews) was 65.1%. The sample studied was similar in structure in terms of age and gender to the population between 18 and 64 years of age in the Madrid region.

Regarding knowledge of risk factors, 92.3% [95% CI: 91.0-93.4] knew that prolonged sun exposure is a risk factor for skin cancer and 73.6% [95% CI: 71.6-75.5] knew about the association of skin cancer with prolonged exposure to UV ray lamps. Table 1 shows the odds ratio (OR) adjusted for gender, age, educational level and employment status. Knowledge of these risk factors was higher among women than among men. For age, no differences were observed for the risk of sun exposure, while knowledge about the effect of artificial UV exposure declined as age increased (p linear trend = 0.007). Knowledge of the effects of both kinds of exposure, natural and artificial, fell in a direct relationship with the reduction of educational level (p linear trend <0.001). Although the frequency with which unemployed people and pensioners stated that they knew of these risk factors was lower, after adjustment there were no statistically significant differences for employment status.

For the use of protective measures to avoid sun exposure in summer, 60.1% of the population interviewed stated that they normally used clothing as sun protection, 78.2% used sun creams and 60.8% sunglasses with protective lenses against UV radiation (Table 2). Women more frequently used sun creams and sunglasses than men, but less frequently used clothing as sun protection. The use of clothing as a protective measure increased with age (p linear trend <0.001). The use of creams was higher among those of 30-44 years of age than among those of 18-29 years of age, estimating an OR of 1.42 [95% CI: 1.03-1.96], whereas there were no age differences for the use of sunglasses. There was less use of creams and sunglasses as the educational level decreased (p linear trend <0.001), but no differences were seen for the use of clothing as a protective measure. For employment status, statistically significant differences were only detected in the adjusted model, with a lower use of sunglasses among students.

Finally, Table 3 shows the prevalence and risk of exposure to UV radiation and sunburn in the last year. Some 14.6% stated that they sunbathed always or nearly always between 12 midday and 4 in the afternoon for tanning, 4.3% used UV ray lamps in the last 12 months and 13.2% suffered sunburn in the last 12 months. The habit of sunbathing in the summer between 12 midday and 4 in the afternoon for tanning was seen more frequently among women and young people. No clear pattern was seen for educational level or employment status. The use of UV ray lamps for tanning was also higher among women. No differences were seen for the use of UV tanning equipment by educational level after adjustment for the rest of the sociodemographic variables. Regarding employment status, a lower use of such equipment was recorded for students. Women reported suffering less sunburn throughout the last year than men, OR of 0.68 [95% CI: 0.51-0.90]. In addition, as age increased the probability of sunburn decreased (p linear trend <0.001). By educational level, those with lower secondary education suffered less frequently from sunburn in the last year (OR of 0.58; 95% CI: 0.39-0.87). By employment status, students were the group that most frequently reported sunburn in the last year, estimating an OR of 1.60 [95% CI: 1.07-2.40].

No statistically significant interactions were found between the variables studied.

The main results of this study suggest that most of the population, especially among people of a higher educational level and women in general, knows the relationship between exposure to UV radiation and skin cancer. The most commonly used protection was sun cream, and a variable distribution was seen by gender, age and educational level, according to the types of measures employed. Some 13.2% suffered sunburn during the last year, with a greater risk detected for men, young people and students.

Knowledge that sun exposure is a risk factor for skin cancer is very high in this population (92.3%), but is lower for artificial UV exposure, with one in four people unaware of the risk. Indeed, this latter estimate is lower compared to that of a recent study in Denmark, where 88% identified artificial UV exposure as a risk factor for cancer and skin alterations,15 or to that shown in the United Kingdom (UK) (82%).16 Nevertheless, the distribution of this knowledge, greater among people of a higher educational level and women in general, is consistent with the pattern detected by Miles et al in the UK.16

The relatively high level of knowledge about the risk of exposure to UV radiation contrasts with the level of use of protective measures. For example, only 60.1% of those interviewed used clothing as sun protection. Although the way of posing the question and of evaluating the replies differs between studies, this prevalence can be compared to that found in Melbourne17 (66%), a city that also has a very high exposure to UV radiation. In other geographical areas, such as the UK16 (38%), the USA18,19 (23%) or Israel20 (11%), the prevalence is very low. In our study, we found that women and young people adopt this protective measure less frequently, a result previously obtained by some authors,18,19,21,22 although others have not detected gender differences.16,23 In contrast to that found in some other areas regarding use of protective measures, in the Madrid region, people with a higher educational level did not use clothing more frequently as sun protection, something that has also been reported for the USA19 and the UK.16

As observed by other authors,22 the use of sun creams is the preferred method for sun protection, probably because, although it is less safe,24–26 it is compatible with sun tanning. The percentage using creams in Madrid (78%) is much higher than in the USA18 (49%) and the UK16 (37%), although in these studies only those using creams with a sun protection factor of 15 or above were considered to be adequately protected. The Madrid percentage is also higher than the estimates for Israel20 (37%) and Melbourne17 (27%). Sun creams were the most commonly used method by women, who were precisely the group least using clothing for sun protection. Regarding age and educational level, creams were most used by interviewees of 30-44 years of age and those with the highest educational level. These results are compatible with those observed in other countries.16,18,19,22 For the use of sunglasses, 61% used sunglasses with protective lenses against UV radiation, a percentage considerably higher than that in Israel (28%).20

As already described in the literature,21 there is a discrepancy between the knowledge that the population has about the risk of sun exposure and the level of protective measures taken to avoid its effects. Our results also show this discrepancy, which is probably due to a certain level of skin tanning still being socially considered to be attractive and an indicator of good health.16,21,27

Exposure to solar radiation in the peak afternoon hours is low (15%), much lower than that recorded in Israel20 (63%). Again, it is associated with women and with young people, as in the UK.28 Similarly, the prevalence of artificial UV exposure is very low in our region (4.3%), at least when compared with countries with limited sun exposure, such as Denmark, with a prevalence of 29%.15 This prevalence is also lower than that in the USA (15%).29 In our study, artificial UV exposure is higher among women and young people, which is consistent with the findings of previous studies.15,27,29,30 Our data do not reflect an association with educational level, in contrast to other studies that have found associations in different directions, in some cases being linked to a lower educational level15 and, in others, to a higher educational level.29

In our study, the prevalence of sunburn in the last year (13.2%) is much lower than that seen in the Anglo-Saxon countries, using the same or a very similar question: 34-39% in the USA,25,31,32 39% in the UK,28 56% in Canada24 or 51-70% in Australia.33,34 In Europe, specifically in Stockholm, a prevalence of 55% has been estimated for the population of 13-50 years of age.30 Factors that could contribute to these differences are that, as previously mentioned, the population of the Madrid region more frequently uses sun protection measures, but also that the dominant skin phototype of the population is more resistant to sun exposure. Hence, for example, when only people of Latin origin were included in the interviews conducted in the USA, the percentage of sunburn was reduced to 20% for men and 17.2% for women.31 Yet in Melbourne, with a less resistant skin phototype, a study published in 2008 showed how the percentage of people suffering sunburn was 9.1% due to the influence of strong prevention campaigns.17

Although women sunbathe more often, they suffer less sunburn than men, a finding consistent with those of other authors.24,25,27,28,31–34 It is possible that the greater use of protective sun creams by women may have influenced these results, although the difference could also be due to variations in total sun exposure times, as in general men spend more time outdoors than women.35 According to our results, the youngest people in the study, who also have a higher sun exposure, have a higher incidence of skin lesions, as indicated in other studies.18,24,25,27,28,32,33,36 Irrespective of age, students have a greater probability of suffering sunburn, as seen in previous reports.32,36 However, no clear association was found between sunburn and educational level, a relationship that has contradictory information in the literature. Although some studies have found no relationship,25,27,28 others have found a greater probability of sunburn for people with the highest educational level,32,36 or for those with a low educational level.33 Finally, there did not appear to be a higher risk of sunburn for employed people, which could suggest that its occurrence is linked to leisure-time sun exposure, looking for a tan.28

There are certain methodological limitations in our study that should be pointed out, in order to obtain a better interpretation of the results. Data have not been obtained for those over 64 years of age, among whom there are many cases of skin cancer, or for those under 18 years of age, where prevention is very important. The general way of measuring the variables has not allowed the gathering of detailed information, for example, about the level of protection of sun creams or the frequency of application, the inclusion of which would be useful in subsequent surveys. Although subject to the classic memory bias of this type of measurement, self-reported information from questionnaires has demonstrated an acceptable validity.37,38 Another limitation is related to the differences in the questions and response categories used in questionnaires, which make comparison between studies difficult, leading to a recent proposal for standardized measurements.14

This study is based on a broad representative sample (in terms of age and gender) of a region that has 13.5% of the population of Spain. Nevertheless, it is possible that people with a low educational level could be underestimated.39 The telephone questionnaire of SIVFRENT (a Behavioural Risk Factor Surveillance System for non-communicable diseases in the Madrid region), in which the section about sun exposure was included, has shown a good reproducibility40 and convergent validity as compared to home surveys.39 Moreover, the distribution of the interviews throughout all the months of the year avoids estimates being influenced by seasonal variability. For example, a higher prevalence of sunburn has been described by those interviewed in the summer.32

In summary, most of the population, especially people with a high level of education and women in general, know the relationship between exposure to UV radiation and skin cancer, even if a discrepancy was seen between this level of knowledge and the use of protective measures and sun exposure habits. The use of sun creams is the most frequently used protective measure, and one in seven people normally sunbathe during the summer in the peak afternoon hours, with this habit being more frequent among women and young people. Some 13.2% of the sample population suffered sunburn in the last year, with a higher risk among men, young people and students. These results indicate the need to maintain preventive strategies to continue improving knowledge about the risk of exposure to UV radiation and reduce risk behaviour to exposure, as well as strengthening environmental protection measures, such as guaranteeing that public recreational spaces have abundant shady areas for protection against direct exposure to the sun.

This study was funded by the Madrid Regional Health Authority, Spain.

I. Galán and E. Cámara designed the study. I. Galán performed statistical analysis. I. Galán, A. Rodríguez, L. Díez and E. Cámara significantly contributed to the interpretation of the data and to the article writing. All authors read and approved the final manuscript.

None declared.