Patterns of solar ultraviolet radiation exposures and melanoma risk in Canada
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Authors
Waddingham, Claudia M.
Date
Type
thesis
Language
eng
Keyword
Solar Ultraviolet Radiation , Melanoma , Canada , Intermittent , Occupational , Chronic
Alternative Title
Abstract
Solar ultraviolet radiation (UVR) exposure is established as the primary cause of cutaneous melanoma. It has been hypothesized that moderate time in the sun and intermittent sun exposure increases the risk of melanoma, while chronic sun exposure has no association or may even decrease the risk of melanoma. The aim of this thesis is to examine the relationship between average time in the sun, sun exposure patterns, residential ambient UVR, and occupational UVR exposure and melanoma risk in Canada. A prospective cohort study, the Canadian Partnership for Tomorrow’s Health, collected self-reported questionnaire data on sun exposure, occupational history, and other melanoma risk factors for three provincial cohorts (Alberta, Ontario, and Quebec). Individuals from the cohorts were linked to cancer registries or administrative datasets to identify melanoma cases. Average time in the sun and residential ambient UVR exposures were investigated using a cohort methodology, while a case-cohort design was utilized to assess occupational solar exposure and risk of melanoma. For assessing occupational solar exposure, an individual’s longest job held was coded to a solar job exposure matrix to assign solar exposure status. Multivariable Cox proportional hazard models with age as the time scale and adjusted for potential confounders were used to estimate hazard ratios for each investigated relationship. Neither average daily time in thesun, intermittent and chronic solar exposure patterns, nor ambient UVR were found to have a statistically significant relationship with melanoma risk. Additionally, occupational solar exposure was not associated with risk of melanoma (HRadj = 0.94; 95% CI = 0.63-1.41). Although this study found typical time in the sun was only suggestive of increasing melanoma risk and occupational solar exposure was not associated with melanoma risk, the results align with existing literature. Understanding how different patterns of solar UVR exposure affect the risk of melanoma among Canadians can help inform on strategies aimed at targeting modifiable solar behaviors to reduce the burden of melanoma.