Ultraviolet Radiation Exposure in High-Risk Populations

Abstract

Skin cancer is the most diagnosed cancer in the United States, and both collegiate athletes and survivors of skin cancer are high-risk groups for future skin cancer diagnoses. While physical activity and exercise, such as gained from participation in an athletic program or a gardening intervention, can potentially reduce incidence of some chronic diseases, the ultraviolet radiation (UVR) exposure which may accompany these activities is the number one modifiable risk factor for all skin cancers. Thus, assessment of UVR exposure is warranted for both high-risk groups. Furthermore, atypical (dysplastic) nevi (AN/DN) are associated with melanoma incidence, and increased UVR exposure likely plays a role in development of these nevi. Assessment of skin lesions in collegiate athletes becomes important as a step towards identifying higher-risk populations in need of closer monitoring. This dissertation outlines results from two different studies in two separate populations. The first two aims focus on assessing trends in sun exposure and sun protection among collegiate athletes and estimating the prevalence of atypical nevi and potential demographic and exposure related factors associated with past diagnosis of these lesions in the athletes (Stanford University SUNSPORT data). The third aim focuses on describing and assessing UVR exposure among skin cancer survivors before and after a community gardening intervention (Harvest for Health Together Arizona). The results from Specific Aim 1 show that 3,564 incoming collegiate athletes who completed a SUNSPORT survey and participated in outdoor sports reported a mean of over 700 hours of outdoor training time per year whereas indoor sport athletes only trained outdoors 27.5 hours per year. Furthermore, there was no statistically significant change in hours training outdoors over the 12 years for either indoor or outdoor athletes. Sun-protection scores showed a statistically significant positive linear increase among outdoor athletes with protection scores increasing 0.57 points per three-year time period (Trend Coefficient: 0.57, 95% CI: 0.45, 0.69), which was contrasted to indoor athletes with a significant negative linear trend in protection, with scores decreasing by 0.39 points per year (Linear Trend Coefficient: -0.39, 95% CI: -0.63, -0.16). In Specific Aim 2, analysis of 1,025 Stanford athletes who reported they received a physician-based full-body skin examination prior to entering Stanford, over 20% reported a previous atypical nevi diagnosis. Prevalence estimates were highest among those athletes with red hair (33.3%). In outdoor athletes, each 50 additional hours of outdoor training time was associated with 6% higher prevalence of atypical nevi diagnosis. Furthermore, a 5% decrease in atypical nevi was observed per one-unit increase in the sun protection score, based on the linear ln(odds ratio (OR)) and those with skin type I (always burn and never tan) had an Odds Ratio (OR)=2.87 for AN/DN as those with phototype VI skin (never burns, tans easily). Specific Aim 3 focused on an analysis of UVR exposure in the 29 people who completed enrollment in pilot study for the Harvest for Health Together Arizona community gardening program. All participants were survivors of skin cancer, either melanoma or non-melanoma skin cancer. UVR exposure was measured at the wrist for seven days at baseline and at study end using dosimeter data. At baseline, participants averaged a total weekly dose of UVR of 268.7 J/m2. The average total dose of UVR decreased significantly after this intervention with an average dose of 111.2 J/m2, p=0.04 (Pre-Post difference= -157.5 J/m2). This research suggests that outdoor collegiate athletes receive high levels of UVR exposure and some of the athletes have high prevalence of a prior atypical nevi diagnosis. This finding suggests a need for interventions to reduce UVR exposure and/or increased surveillance among this group, particularly for those athletes at highest risk. Furthermore, this analysis suggests that cancer survivors may be able to participate in a community gardening intervention designed to improve diet and activity levels without significantly increasing their exposure to UVR. Such interventions might then reduce the incidence of Type Two diabetes and other chronic diseases including secondary cancers.