Ekström Smedby K et al. (2005) Ultraviolet radiation exposure and risk of malignant lymphomas. J Natl Cancer Inst 97: 199–209

A recent study by Ekström Smedby and colleagues has investigated the rapid increase in the incidence of malignant lymphomas. Surprisingly, the results suggest that exposure to ultraviolet radiation might reduce the risk of developing these tumors.

The Scandinavian Lymphoma Etiology (SCALE) study used a telephone interview to assess the history of sun exposure and other factors in 3,740 adults with a first, newly diagnosed malignant lymphoma. The analysis also included 3,187 control subjects, matched for age and sex. All participants were from Denmark or Sweden and were under 75 years old.

The risk of non-Hodgkin's lymphoma was 30–40% lower in those who reported a history of frequent sunbathing, sunburn, or 'sun vacations abroad' than in those who had had lower UV exposure (P <0.01). A similar, inverse relationship was also found between UV exposure and the risk of Hodgkin's lymphoma, although this association was weaker. As expected, those with a self-reported history of skin cancer were at increased risk of Hodgkin's and non-Hodgkin's lymphoma.

In conclusion, these unexpected results suggest a negative association between UV exposure and malignant lymphoma risk. The link between skin cancer and these tumors is, therefore, likely to be independent of UV exposure. Ekström Smedby et al. call for further epidemiologic studies and research into the underlying mechanisms by which UV exposure might reduce the risk of malignant lymphoma.