Factors associated with the prevalence of atypical nevus in a Mediterranean pigmented skin lesion clinic

Defining "intermittent UVR exposure"

BACKGROUND

Cutaneous malignant melanoma (CMM) has been associated with "intermittent UVR exposure", which in previous studies has mainly been assessed by retrospective questionnaire data. Further, there is no uniform definition of the term "intermittent UVR exposure".

OBJECTIVES

We aimed to define and quantify "intermittent UVR exposure" by an objective measure.

METHODS

A broad study population of adults and children had data collected during a summer period. Data were personal UVR dosimetry measurements, from which the number of "intermittent days" was derived, sun behaviour diaries and retrospective questionnaires. Two definitions of intermittent UVR exposure were tested: (1) days when UVR dose exceeded 3 times individual average daily UVR dose, and (2) days when UVR dose exceeded individual constitutive skin type. Measures of nevi and lentigines were used as surrogates for CMM.

RESULTS

Using the first definition based solely on UVR dosimetry data we found 1241 "intermittent days" out of a total of 17 277 days (7.2%) among 148 participants. The numbers for nevi and lentigo density were significantly predicted by the number of intermittent days (R(2) = 0.15 and R(2) = 0.40, p < 0.001). The corresponding numbers for prediction of nevi and lentigo density by retrospective questionnaire data was lower (R(2) = 0.11, R(2) = 0.26, p < 0.001).

CONCLUSIONS

We introduce a well-defined objective measure of intermittent UVR exposure. This measure may provide a better prediction of solar skin damage and CMM than retrospective questionnaire data.

Patterns and timing of sunlight exposure and risk of basal cell and squamous cell carcinomas of the skin--a case-control study

BACKGROUND

Non-melanoma skin cancer (NMSC), comprised of basal (BCC) and squamous (SCC) cell carcinomas, is the most common cancer in Caucasians. Ultraviolet radiation (UVR) exposure is the most important environmental risk factor for NMSC. However, the precise relationship between UVR and the risk of NMSC is complex, and the relationship may differ by skin cancer type.

METHODS

A case-control study was conducted among Florida residents to investigate measures of patterns (intermittent vs. continuous) and timing (childhood vs. adulthood) of sunlight exposure in BCC and SCC. Participants included 218 BCC and 169 SCC cases recruited from a university dermatology clinic and 316 controls with no history of skin or other cancers.

RESULTS

A history of blistering sunburn (a measure of intermittent sunlight exposure) was associated with both BCC (OR = 1.96, 95% CI = 1.27-3.03) and SCC (OR = 2.02, 95% CI = 1.22-3.33). Additionally, having a job in the sun for ≥ 3 months for 10 years or longer (a measure of continuous sunlight exposure) was also associated with both BCC and SCC in our study population. With the exception of younger age at first blistering sunburn, measures of younger age at sunlight exposure tended to be associated with SCC, but not BCC risk.

CONCLUSIONS

Results from the current study suggest that sunlight exposure is associated with both BCC and SCC risk regardless of the pattern in which the exposure was received (i.e. intermittent vs. continuous). The data also suggest that sunlight exposure at a younger age may be more important for SCC but not BCC, however additional studies are needed to further characterize sunlight exposure-response relationships in different types of NMSC.