Relationship between ambient ultraviolet radiation and Hodgkin lymphoma subtypes in the United States

Background: There are few modifiable risk factors for Hodgkin lymphoma (HL), the most common cancer among young adults in Western populations. Some studies have found a reduced risk with exposure to ultraviolet radiation (UVR), but findings have been inconsistent and limited to HL as a group or the most common subtypes. Methods: We evaluated UVR and incidence of HL subtypes using data from 15 population-based cancer registries in the United States from 2001 to 2010 (n = 20 021). Ground-based ambient UVR estimates were linked to county of diagnosis. Incidence rate ratios (IRRs) and 95% confidence intervals (CIs) were calculated for UVR quintiles using Poisson regression models adjusted for age, sex, race/ethnicity, diagnosis year, and registry. Results: Hodgkin lymphoma incidence was lower in the highest UVR quintile for nodular sclerosis (IRR = 0.84, 95% CI = 0.75-0.96, P-trendo0.01), mixed cellularity/lymphocyte-depleted (IRR = 0.66, 95% CI = 0.51-0.86, P-trend = 0.11), lymphocyte-rich (IRR = 0.71, 95% CI = 0.57-0.88, P-trendo0.01), and nodular lymphocyte predominant HL (IRR = 0.74, 95% CI = 0.56-0.97, P-trendo0.01), but 'not otherwise specified' HL (IRR = 1.19, 95% CI = 0.96-1.47, P-trend = 0.11). Conclusions: This is the largest study of UVR and HL subtypes covering a wide range of UVR levels; however, we lack information on personal UVR and other individual risk factors. These findings support an inverse association between UVR and HL.