Exposure to ultraviolet radiation and risk of malignant lymphoma and multiple myeloma--a multicentre European case-control study.

BACKGROUND: Three recent studies have reported a decreased risk of non-Hodgkin lymphoma (NHL) for high ultraviolet (UV) radiation exposure.
METHODS: We conducted a multicentre case-control study during 1998-2004 in France, Germany, Ireland, Italy and Spain, comprising 1518 cases of NHL, 268 cases of Hodgkin lymphoma, 242 cases of multiple myeloma and 2124 population or hospital controls. We collected information on sensitivity to sun and personal exposure to UV radiation in childhood and adulthood via interview, and assessed occupational exposure to UV radiation from the occupational history.
RESULTS: The risk of Hodgkin and NHL was increased for increasing skin sensitivity to the sun [odds ratio (OR) for no suntan vs very brown 2.35, 95% CI 0.94-5.87 and 1.39, 95% CI 1.03-1.87, respectively]. The risk of diffuse large B-cell lymphoma was reduced for increasing adult personal (OR for highest vs lowest quartile of exposure in free days 0.62, 95% CI 0.44-0.87) and for occupational exposure to UV radiation (OR for highest vs lowest exposure tertile 0.63, 95% CI 0.37-1.04). The risk of multiple myeloma was increased for personal exposure to UV radiation during adulthood (OR for highest vs lowest quartile of exposure in free days 1.49, 95% CI 0.88-2.50). A protective effect was observed for use of sun lamps for diffuse large B-cell lymphoma (OR for 25+ times vs never 0.63, 95% CI 0.38-1.03).
CONCLUSIONS: The hypothesis of a protective effect of UV radiation on lymphoma is supported by our results. The underlying mechanisms might differ from those operating in skin carcinogenesis. The increased risk of multiple myeloma is worth replication.