Urinary thymidine dimer excretion reflects personal ultraviolet radiation exposure levels.

Exposure to ultraviolet radiation (UVR) leads to skin DNA damage, specifically in the form of cyclobutane pyrimidine dimers, with thymidine dimers being the most common. Quantifying these dimers can indicate the extent of DNA damage resulting from UVR exposure. Here, a new liquid chromatography-mass spectrometry (LC-MS) method was used to quantify thymidine dimers in the urine after a temporary increase in real-life UVR exposure. Healthy Danish volunteers (n = 27) experienced increased UVR exposure during a winter vacation. Individual exposure, assessed via personally worn electronic UVR dosimeters, revealed a mean exposure level of 32.9 standard erythema doses (SEDs) during the last week of vacation. Morning urine thymidine dimer concentrations were markedly elevated both 1 and 2 days post-vacation, and individual thymidine dimer levels correlated with UVR exposure during the last week of the vacation. The strongest correlation with erythema-weighted personal UVR exposure (Power model, r2 = 0.64, p < 0.001) was observed when both morning urine samples were combined to measure 48-h thymidine dimer excretion, whereas 24-h excretion based on a single sample provided a weaker correlation (Power model, r2 = 0.55, p < 0.001). Sex, age, and skin phototype had no significant effect on these correlations. For the first time, urinary thymidine dimer excretion was quantified by LC-MS to evaluate the effect of a temporary increase in personal UVR exposure in a real-life setting. The high sensitivity to elevated UVR exposure and correlation between urinary excretion and measured SED suggest that this approach may be used to quantify DNA damage and repair and to evaluate photoprevention strategies.

Non-preventable cases of breast, prostate, lung, and colorectal cancer in 2050 in an elimination scenario of modifiable risk factors.

Most Western countries have increasing number of new cancer cases per year. Cancer incidence is primarily influenced by basically avoidable risk factors and an aging population. Through hypothetical elimination scenarios of multiple major risk factors for cancer, we estimated the number of new cancer cases that are non-preventable in 2050. We compare numbers of new postmenopausal breast, prostate, lung, and colorectal cancer cases in 2021 to projected numbers of new cases in 2050 under prevention scenarios regarding smoking, overweight and obesity, and alcohol consumption: no intervention, 50%, and 100% instant reduction. Cancer incidence data were derived from NORDCAN, and risk factor prevalence data from the Danish National Health Survey. Cancer projections were calculated with the Prevent program. Hypothetical 100% instant elimination of major risk factors for cancer in Denmark in 2022 will result in unchanged numbers of new breast and colorectal cancers in 2050. The number of new prostate cancers will increase by 25% compared to 2021. Unchanged risk factor levels will result in noticeable increase in cancer burden. Increase in life expectancy and age will entail an increase in cancer incidence, despite maximum effect of preventive actions in the population. Our results are important when planning future health care.

Updated fraction of cancer attributable to lifestyle and environmental factors in Denmark in 2018.

Environmental exposures and avoidable risk factors account for a large proportion of cancer burden. Exposures and lifestyle vary over time and between populations, which calls for updated and population-specific quantification of how various avoidable risk factors influence cancer risk to plan and design rational and targeted prevention initiatives. The study considered 12 risk-factor groups categorized as class I carcinogens by IARC/WCRF. Exposure data was derived from national studies and surveys and were linked to cancer incidence in 2018 based on the nationwide Danish Cancer Registry. In 2018, 23,078 men and 21,196 women were diagnosed with cancer excluding non-melanoma skin cancer, in Denmark. Of these, 14,235 (32.2%) were estimated to be attributable to avoidable class I carcinogens. Tobacco smoking accounted for 14.6% of total cancers, followed by UV-radiation that accounted for 5.8%. Based on exposure data from 2008, one-third of the cancers in Denmark in 2018 are estimated to be caused by class I carcinogens with tobacco use being the main contributor followed by UV-radiation. Our results should be integrated with public health policies to effectively increase awareness and promote strategies to decrease risk factor exposures at population level.

Novel sunprotection interventions to prevent skin cancer: A randomized study targeting Danes going on vacation to destinations with high UV index.

BACKGROUND: In Denmark, 16,500 cases of melanoma and keratinocyte cancers were registered in 2015, of which 90% could have been avoided by behavioral changes. We aimed to test novel interventions in a randomized design. The interventions targeted Danes going on vacation to high UVI destinations aiming to decrease sunburn by increasing use of sun protection to prevent skin cancer in the Danish population. METHODS: We report a randomized behavioral intervention during May-Dec 2018 with 1548 Danish adults on vacation in 2018 for a period of 1-3 weeks. The study population was population-based and aged 18-65 years. We tested two protection routines against minimal intervention control group (2-by2-factorial design): 1) Avoidance of the sun during peak hours and shade, use of the UV-index and planning of indoor/outdoor activity respectively and, 2) Coverage by increasing use of the hat advice and increasing sunscreen amount by application routine. Outcome was use of protection and sunburn. RESULTS: There were no differences in sunburn prevalence between intervention and control groups. Protection routine 1 and 2 both increased the overall protection score compared to non-users. Protection routine 1 increased the reported use of shade and decreased time exposed in the sun. Protection routine 2 increased the use of hat and sunscreen amount. CONCLUSION: Simple measures can help avoid the majority of one of the most widespread cancers worldwide. Vacations to high UVI destinations is a major influence on the annual Danish UV-exposure. We influenced travelers to protect themselves better and to increase sun protection behavior.

Association of Indoor Tanning Regulations With Health and Economic Outcomes in North America and Europe.

Importance: UV radiation emissions from indoor tanning devices are carcinogenic. Regulatory actions may be associated with reduced exposure of UV radiation at a population level. Objective: To estimate the long-term health and economic consequences of banning indoor tanning devices or prohibiting their use by minors only in North America and Europe compared with ongoing current levels of use. Design, Setting, and Participants: This economic analysis modeled data for individuals 12 to 35 years old in North America and Europe, who commonly engage in indoor tanning. A Markov cohort model was used with outcomes projected during the cohort's remaining life-years. Models were populated by extracting data from high-quality systematic reviews and meta-analyses, epidemiologic reports, and cancer registrations. Main Outcomes and Measures: Main outcomes were numbers of melanomas and deaths from melanoma, numbers of keratinocyte carcinomas, life-years, and health care and productivity costs. Extensive sensitivity analyses were performed to assess the stability of results. Results: In an estimated population of 110 932 523 in the United States and Canada and 141 970 492 in Europe, for the next generation of youths and young adults during their remaining lifespans, regulatory actions that ban indoor tanning devices could be expected to gain 423 000 life-years, avert 240 000 melanomas (-8.2%), and avert 7.3 million keratinocyte carcinomas (-7.8%) in North America and gain 460 000 life-years, avert 204 000 melanomas (-4.9%), and avert 2.4 million keratinocyte carcinomas (-4.4%) in Europe compared with ongoing current levels of use. Economic cost savings of US $31.1 billion in North America and €21.1 billion (US $15.9 billion) in Europe could occur. Skin cancers averted and cost savings after prohibiting indoor tanning by minors may be associated with one-third of the corresponding benefits of a total ban. Conclusions and Relevance: Banning indoor tanning may be associated with reduced skin cancer burden and health care costs. Corresponding gains from prohibiting indoor tanning by minors only may be smaller.

Benefit-Cost Analysis of the Danish Sun Safety Campaign 2007-2015: Cost Savings from Sunburn and Sunbed Use Reduction and Derived Skin Cancer Reductions 2007-2040 in the Danish Population.

BACKGROUND: Ninety percent of skin cancers are avoidable. In Denmark, 16,500 cases of melanoma and keratinocyte cancers were registered in 2015. The Danish Sun Safety Campaign has campaigned since 2007, targeting overexposure to ultraviolet radiation. During 2007-2015, the key indicators of skin cancer, i.e. sunbed use and sunburn, showed annual reductions of 6% and 1%, respectively. OBJECTIVES: We aimed to examine the financial savings to society as a result of the campaign reductions in skin cancer cases (2007-2040), and to examine the campaign's cost-benefit and return on investment (ROI). METHODS: The analysis is based on existing data: (1) annual population-based surveys regarding the Danish population's behavior in the sun; (2) skin cancer projections; (3) relative risks of skin cancers from sunburn and sunbed use and (4) historical cancer incidences, combined with new data; (5) benefits from the avoided costs of skin cancer reductions; and (6) the costs of the Danish Sun Safety Campaign. RESULTS: The results were based on a reduction of 9000 skin cancer cases, saving €29 million of which €13 million were derived from sunburn reductions and €16 million from reductions in sunbed use. The ROI was €2.18. CONCLUSION: Skin cancer prevention in Denmark is cost effective. Every Euro spent by the Danish Sun Safety Campaign saved the Danish health budget €2.18 in health expenses.

Correction to: Benefit-Cost Analysis of the Danish Sun Safety Campaign 2007-2015: Cost Savings from Sunburn and Sunbed Use Reduction and Derived Skin Cancer Reductions 2007-2040 in the Danish Population.

Abstract, Results, first sentence, which previously read: "The results were based on a reduction of 9000 skin cancer cases, saving €47 million of which €29 million were derived from sunburn reductions and €16 million from reductions in sunbed use."

Visual scales are superior to questionnaires in skin phototype self-assessment by children.

BACKGROUND/PURPOSE: There are no suitable methods for skin phototype self-assessment by children. Our study investigated several skin phototype self-assessment methods in children to identify the best correlation to objectively measure skin phototype. METHODS: Danish schoolchildren (ages 6-19) participated in a nation-wide study that assessed skin, eye, hair colour and sun behaviour. Skin phototype self-assessment was performed by children using two visual colour scales (cartoon faces and colour cards), question-based colour scale and questions about tendency to burn and ability to tan. For objective skin phototype measurements, 483 children from all age groups were selected and their pigment protection factor (PPF) was measured at three skin sites using a skin reflectance spectrophotometer. RESULTS: Cartoon faces (r2  = 0.654) and colour cards (r2  = 0.659) were better at predicting PPF on the inner forearm than the question-based colour method (r2  = 0.520). PPF prediction from questions on skin reaction to sun exposure was markedly inferior (r2  ≤ 0.142) to both visual colour scales and question-based colour method. CONCLUSION: Both visual colour scales proved to be superior to question-based skin phototype self-assessment in schoolchildren. In contrast, questions on skin reaction to sun exposure were shown to be an unsuitable tool for self-assessment of skin phototype in children.

Association between sunburn and demographic factors and health behaviour among Danish students.

Sunburn is associated with an increased risk for skin cancer. Denmark has one of the highest incidences of melanoma in the world, although it is a relatively northern country. The objective of this study was to determine whether sunburn is associated with demographic factors and health behaviour among young Danes. Cross-sectional data of >55,000 15- to 25-year-old students participating in the Danish National Youth Study were collected in 2014. Multilevel logistic regression analysis was used to determine associations. Overall, 45% of the students had experienced at least one sunburn in Denmark, and 60% had experienced one sunburn abroad in the past year. Females had higher odds for sunburns than males. Education and geographical region were associated with sunburn but with opposite trends related for sunburn experienced in Denmark and abroad. Students who had poor dietary habits (only abroad), indulged in binge-drinking, smoked (only in Denmark), and more physical activity (only abroad) had higher odds for having a sunburns. We conclude that sunburn is prevalent among young Danes, especially those travelling abroad. Although we found some associations with demographic factors and health behaviour, there were no evident tendencies, thus indicating that broad population-based campaigning should be the preferred intervention.

Skin cancer projections and cost savings 2014-2045 of improvements to the Danish sunbed legislation of 2014.

BACKGROUND: Sunbed use increases the risk of skin cancer. The Danish sunbed legislation (2014) did not include an age limit. AIM: To model skin cancer incidences and saved costs from potential effects of structural interventions on prevalence of sunbed use. MATERIALS AND METHODS: Survey data from 2015 were collected for 3999 Danes, representative for the Danish population in regards to age, gender and region. Skin cancer incidences were modelled in the Prevent program, using population projections, historic cancer incidence, sunbed use exposure and relative risk of sunbed use on melanoma. RESULTS: If structural interventions like an age limit of 18 years for sunbed use or complete ban had been included in the Danish sunbed legislation in 2014, it would have reduced the annual number of skin cancer cases with 455 or 4177, respectively, while for the entire period, 2014-2045 the total reductions would be 3730 or 81 887 fewer cases, respectively. The cost savings from an age limit or ban, respectively, are 9 and 129 millions € during 2014-2045. CONCLUSION: Legislative restrictive measures which could reduce the sunbed use exists. Danish politicians have the opportunity, supported by the population, to reduce the skin cancer incidence and thereby to reduce the future costs of skin cancer.

Vitamin D Status and Seasonal Variation among Danish Children and Adults: A Descriptive Study.

The aim of the present study was to describe vitamin D status and seasonal variation in the general Danish population. In this study, 3092 persons aged 2 to 69 years (2565 adults, 527 children) had blood drawn twice (spring and autumn) between 2012 and 2014. A sub-sample of participants had blood samples taken monthly over a year. Serum 25-hydroxyvitamin D (25(OH)D) concentrations were measured by liquid chromatography mass spectrometry, and information on supplement use was assessed from questionnaires. Seasonal variations in 25(OH)D concentrations were evaluated graphically and descriptively, and status according to age, sex, and supplement use was described. It was found that 86% of both adults and children were vitamin D-sufficient in either spring and or/autumn; however, many had a spring concentration below 50 nmol/L. A wide range of 25(OH)D concentrations were found in spring and autumn, with very low and very high values in both seasons. Among adults, women in general had higher median 25(OH)D concentrations than men. Furthermore, vitamin D supplement use was substantial and affected the median concentrations markedly, more so during spring than autumn. Seasonal variation was thus found to be substantial, and bi-seasonal measurements are vital in order to capture the sizable fluctuations in vitamin D status in this Nordic population.

Development in sunburn 2007-2015 and skin cancer projections 2007-2040 of campaign results in the Danish population.

Exposure to ultraviolet radiation is the main risk factor for skin cancer. Denmark has one of the highest incidences of skin cancer in the world. In 2007, a long-term sun safety campaign was launched in Denmark. We have evaluated the effects on prevalence of sunburn and modeled the effects on future melanoma incidence.Sunburn was evaluated by annual cross-sectional surveys representative for the Danish population on age, gender, and region. During 2007-2015, survey data were collected for 33.315 Danes. Cutaneous Melanoma incidences were modeled in the Prevent program, using population projections, historic incidence, sunburn exposure, and relative risk of sunburn on melanoma.The prevalence of sunburn in Denmark was reduced with 1% annually during 2007 to 2015. The campaign is estimated to have reduced the number of skin cancer cases with 664 annually in 2040 and 14.326 totally during 2007 to 2040. If the campaign was terminated in 2015 and sunburn rates return to precampaign level there would be no annual reduction in 2040 while in total the reduction would be 4.024 cases for 2007 to 2040. A continuous campaign until 2040 would yield annual reductions of 2.121 cases by 2040 and a total of 29.729 cases for the entire period.We have showed the value of prevention and the value of long-term planning in prevention campaigning. Sunburn use was reduced significantly during 2007-2015 and further reductions are possible. Consequently, we predict significant fewer skin cancer cases as anticipated.

Sunbed use 2007-2015 and skin cancer projections of campaign results 2007-2040 in the Danish population: repeated cross-sectional surveys.

OBJECTIVE: To evaluate the effect of the Danish Sun Safety Campaign 2007-2015 on the prevalence of sunbed use and to model future effects on the skin cancer incidences 2007-2040. DESIGN: The study has a repeated, cross-sectional design. SETTING: Exposure to ultraviolet radiation is the main risk factor for skin cancer. Denmark has the highest prevalence of sunbed use reported and one of the highest incidences of skin cancer worldwide. PARTICIPANTS: During 2007-2015, survey data were collected for 37 766 Danes, representative of the Danish population with regards to age, gender and region. INTERVENTIONS: In 2007, an ongoing long-term antisunbed campaign was launched in Denmark. PRIMARY AND SECONDARY OUTCOME MEASURES: Sunbed use was evaluated by annual cross-sectional surveys. Skin cancer incidence was modelled in the Prevent programme, using population projections, historic cancer incidence, sunbed use exposure and relative risk of sunbed use on melanoma. RESULTS: The prevalence of recent sunbed use in Denmark was reduced from 32% and 18% to 13% and 8% for women and men, respectively. The campaigns results during 2007-2015 are estimated to reduce the number of skin cancer cases from more than 5000 (746malignant melanoma, 1562 SCC, 2673 BCC) totally during 2007-2040. Keeping the 2015 level of sunbed use constant by continued campaign pressure or introduction of structural interventions would potentially prevent more than 750 skin cancer cases annually in 2040 and 16 000 skin cancer cases in total during 2007-2040. CONCLUSION: We have shown the value of prevention and of long-term planning in prevention campaigning. Sunbed use was reduced significantly during 2007-2015 and further reductions are possible by structural interventions. Consequently, significantly fewer skin cancer cases are anticipated during 2007-2040. The Danish Parliament has population support to enforce structural interventions to avoid a large burden of this disease.

Avoidable colorectal cancer cases in Denmark - The impact of red and processed meat.

BACKGROUND: High red and processed meat intakes are associated with increased colorectal cancer (CRC) risk. The effect of eliminating or reducing red and processed meat consumption on CRC burden was not previously quantified in Denmark. The aim of this study was to calculate the possible effects of reductions in red and processed meat consumption on future CRC incidence in the Danish adult population. METHODS: Under six scenarios of prevalence exposure (meat consumption) the number of CRC cases in Denmark for a 30-year period (2016-2045) was estimated and compared to the projected number of CRCs if the prevalence of meat consumption remains constant. Data was obtained from the NORDCAN register, Statistics Denmark, and from the Danish dietary survey data (DANSDA). Analyses were conducted using the Prevent model. RESULTS: During the 30-year period, a total of 36,767 (19.8%) CRC cases out of 185,937 expected could be avoided in Denmark by eliminating the consumption of both red and processed meat. For the same period, a modest reduction in both red and processed meat consumption could lead to the prevention of 16,964 (9.1%) CRC cases. The greatest reductions were seen among men, and the highest impact was estimated for the elimination or reduction of processed meat consumption. CONCLUSION: Decreased red and processed meat consumption could reduce the burden of CRC markedly in Denmark. These results can assist public health planners and help highlight the important role of a modest but realistic reduction in meat consumption in the prevention of CRC.

Solar UV exposure among outdoor workers in Denmark measured with personal UV-B dosimeters: technical and practical feasibility.

BACKGROUND: Exposure to solar ultraviolet radiation is a well-known cause of skin cancer. This is problematic for outdoor workers. In Denmark alone, occupational skin cancer poses a significant health and safety risk for around 400,000 outdoor workers. Objective measures of solar ultraviolet radiation exposure are needed to help resolve this problem. This can be done using personal ultraviolet radiation dosimeters. METHODS: We consider technical and practical feasibility of measuring individual solar ultraviolet exposure at work and leisure in professions with different á priori temporal high-level outdoor worktime, using aluminium gallium nitride (AlGaN) photodiode detector based personal UV-B dosimeters. Essential technical specifications including the spectral and angular responsivity of the dosimeters are described and pre-campaign dosimeter calibration applicability is verified. The scale and conduct of dosimeter deployment and campaign in-field measurements including failures and shortcomings affecting overall data collection are presented. RESULTS: Nationwide measurements for more than three hundred and fifty workers from several different professions were collected in the summer of 2016. On average, each worker's exposure was measured for a 2-week period, which included both work and leisure. Data samples of exposure at work during a Midsummer day show differences across professions. A construction worker received high-level occupational UV exposure most of the working day, except during lunch hour, accumulating to 5.1 SED. A postal service worker was exposed intermittently around noon and in the afternoon, preceded by no exposure forenoon when packing mail, accumulating to 1.6 SED. A crane fitter was exposed only during lunch hour, accumulating to 0.7 SED. These findings are in line with our specialist knowledge as occupational physicians. CONCLUSIONS: Large-scale use of personal UV-B dosimeters for measurement of solar ultraviolet radiation exposure at work and leisure in Denmark is indeed feasible from a technical and practical viewpoint. Samples of exposure data shown support the presumption that the Danish campaign UV-B dosimeter measurement dataset can be used to sum and compare exposure between groups of professions with reliable results to be used in future analysis with clinical as well as epidemiological/questionnaire data. This was despite some dosimeter failures and shortcomings.

Knowledge deficit, attitude and behavior scales association to objective measures of sun exposure and sunburn in a Danish population based sample.

The objective of this study was to develop new scales measuring knowledge and attitude about UVR and sun related behavior, and to examine their association to sun related behavior objectively measured by personal dosimetry. During May-August 2013, 664 Danes wore a personal electronic UV-dosimeter for one week that measured their UVR exposure. Afterwards, they answered a questionnaire on sun-related items. We applied descriptive analysis, linear and logistic regression analysis to evaluate the associations between the questionnaire scales and objective UVR measures. Perceiving protection as routine and important were positively correlated with protective behavior. Knowledge deficit of UV and risk of melanoma, perceived benefits and importance of protection behavior was also correlated with use of protection. 'Knowledge deficit of UV and risk of melanoma and Perceived barrier towards sun avoidance between 12 and 15' were both associated with increased risk of sunburn. Attitude towards tan was associated to both outdoor time and exposure as well as use of protection, but not to sunburn. The results regarding Knowledge deficit of UV and risk of melanoma associated to UVR exposure and Perceived barrier towards sun avoidance between 12 and 15 emphasize the importance of awareness of melanoma risk and the priority of the skin cancer prevention advice. Shifting activities to outside the suns peak-hours could be an approach for structural and campaign preventive measures. Knowledge of items predicting exposure to UVR, use of protection and sunburn are important for planning of preventive interventions and melanoma research.

Sunbed use among 64,000 Danish students and the associations with demographic factors, health-related behaviours, and appearance-related factors.

Sunbed use is associated with an increased risk for skin cancer and is particularly dangerous for younger persons. The objective of this study was to assess how demographic factors, health-related behaviours and appearance-related factors are associated with sunbed use. Cross-sectional data from the Danish National Youth Study collected by the National Institute of Public Health during 2014 was used. A total of 64,382 students aged 15-25years were included in the present study. Multilevel logistic regression analyses were used to determine associations. Sunbed use during the past 12months was reported by 22% of students, with a higher proportion among females (29%) than males (12%). Factors associated with sunbed use were older age, studying at a vocational college or a higher preparatory examination school compared to upper secondary school, and lower parental education. Furthermore, being a smoker, been binge-drinking, longer duration of exercise and been dieting were also associated with sunbed use. For females, poor dietary habits were also associated with sunbed use. Feeling overweight was associated with lower odds for sunbed use for males, but with higher odds for females. Lower body satisfaction was associated with higher odds of sunbed use, except for overweight males. Students who were underweight had lower odds for sunbed use, than normal weight students. Conclusively, we found evidence of associations between demographic factors, health-related behaviours and appearance-related factors and sunbed use. Understanding these relations could help to identify high-risk groups and guide preventive strategies for sunbed use and skin cancer prevention.

YouTube as a source of health information: Analysis of sun protection and skin cancer prevention related issues.

Although social media ubiquitously supplementstraditional information sources such as newspapers,magazines, radio, and television, investigation of onlinehealth information related to sun protection and skincancer prevention has been scarce and largely limitedto English language sources. Using the search terms"sun protection," "sunscreen," "skin cancer prevention,""tanning bed" and "vitamin D," we investigated 281YouTube videos presented in 6 languages: English,German, French, Spanish, Swedish, and Danish. Foreach video, we used a four-sectioned checklist toassess general information, popularity, expert drivenmeasures, and heuristic driven measures. Differencesbetween languages were detected: English languagevideos were most frequently viewed (median numberof views: 5488 compared to 248 -1591 in otherlanguages). Approximately 60% of videos revealednegative effects of solar ultraviolet (UV)-exposure.The majority of videos (75%) targeted adults. Videoson tanning beds and sunscreen contained false ormisleading information 40% and 20% of the time,respectively. We confirm observations made withrespect to other medical disciplines that the generalquality of YouTube contributions is often inferiorand does not deliver sustainable information. Othersources of information should be included whensearching for health information online.

Effects of smartphone diaries and personal dosimeters on behavior in a randomized study of methods to document sunlight exposure.

Dosimeters and diaries have previously been used to evaluate sun-related behavior and UV exposure in local samples. However, wearing a dosimeter or filling in a diary may cause a behavioral change. The aim of this study was to examine possible confounding factors for a questionnaire validation study. We examined the effects of wearing dosimeters and filling out diaries, measurement period and recall effect on the sun-related behavior in Denmark in 2012. Our sample included 240 participants eligible by smartphone status and who took a vacation during weeks 26-32 in 2012, randomized by gender, age, education and skin type to six groups: 1) Control + diary, 2) Control, 3) 1-week dosimetry measurement, 4) 1-week dosimetry measurement + diary, 5) 3-week dosimetry measurement and 6) 1-week dosimetry measurement with 4 week delayed questionnaire. Correlation coefficients between reported outdoor time and registered outdoor time for groups 3-6 were 0.39, 0.45, 0.43 and 0.09, respectively. Group 6 was the only group not significantly correlated. Questionnaire reported outdoor exposure time was shorter in the dosimeter measurement groups (3-6) than in their respective controls. We showed that using a dosimeter or keeping a diary seems to increase attention towards the behavior examined and therefore may influence this behavior. Receiving the questionnaire with 4 week delay had a significant negative influence on correlation and recall of sunburn. When planning future UV behavior questionnaire validations, we suggest to use a 1-week interval for dosimetry measurements, no diary, and to minimize the time from end of measurement to filling out questionnaires.