OBJECTIVES:To explore whether the inverse association of sun exposure with non Hodgkin lymphoma among adults is also evident among the childhood population and test the specificity of the relation by contrasting the findings to those for Hodgkin lymphoma.

METHODS:A total of 87 cases of childhood (0-14 years) with non Hodgkin lymphoma and 71 with Hodgkin lymphoma, diagnosed in Greece through the national network of childhood Hematology-Oncology Units, during a 7-year period, along with 164 age- and gender-matched control children were enrolled in the study. The guardians of all eligible children were interviewed in person on the basis of a structured questionnaire covering socio-demographic, anthropometric, and perinatal characteristics. Average time of sunbathing per year at a seaside resort was used as a proxy variable of exposure to sun controlling for use of sun protection measures.

RESULTS:The estimated incidence of 10.2 cases per 1,000,000 children-years {95% Confidence Intervals (CI), 8.4-12.1} for NHL during the study period in Greece is around the average figure in countries of the European Union. There was an inverse association of sun exposure with Non Hodgkin lymphoma, namely, for an increment of 15 days of sunbathing at seaside resorts children had almost 40% lower risk (Odds Ratio: 0.60, 95% CI: 0.43-0.83), whereas no such association was evident for Hodgkin lymphoma. The risk for non Hodgkin lymphoma has been found to be statistically and significantly higher in birth weight (Odds ratio: 1.42 and 95% CI, 1.04-1.92, for every 500 g increment), whereas there was no substantial indication that maternal education or maternal smoking during the child's life were important risk factors for the disease.

CONCLUSIONS:This is the first study to provide epidemiological evidence that increased sun exposure of children may also be associated with a decreased risk of developing childhood non Hodgkin, but not Hodgkin lymphoma.

BACKGROUND:The incidence of malignant lymphomas has been increasing rapidly, but the causes of these malignancies remain poorly understood. One hypothesis holds that exposure to ultraviolet (UV) radiation increases lymphoma risk. We tested this hypothesis in a population-based case-control study in Denmark and Sweden.

METHODS:A total of 3740 patients diagnosed between October 1, 1999, and August 30, 2002, with incident malignant lymphomas, including non-Hodgkin lymphoma, chronic lymphocytic leukemia, and Hodgkin lymphoma, and 3187 population controls provided detailed information on history of UV exposure and skin cancer and information on other possible risk factors for lymphomas. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated by logistic regression. Statistical tests were two-sided.

RESULTS:Multivariable-adjusted analyses revealed consistent, statistically significant negative associations between various measures of UV light exposure and risk of non-Hodgkin lymphoma. A high frequency of sun bathing and sunburns at age 20 years and 5-10 years before the interview and sun vacations abroad were associated with 30%-40% reduced risks of non-Hodgkin lymphoma (e.g., for sunbathing four times a week or more at age 20 versus never sunbathing, OR = 0.7, 95% CI = 0.6 to 0.9; for two or more sunburns a year at age 20 versus no sunburns, OR = 0.6, 95% CI = 0.5 to 0.8). These inverse associations increased in strength with increasing levels of exposure (all P(trend)

CONCLUSIONS:A history of high UV exposure was associated with reduced risk of non-Hodgkin lymphoma. The positive association between skin cancer and malignant lymphomas is, therefore, unlikely to be mediated by UV exposure.

Animal and human studies support a protective effect of vitamin D sufficiency related to malignancy by uncovering paracrine and autocrine effects of extra-renal 25-hydroxyvitamin D (25(OH)D) activation including regulation of cell cycle proliferation, apoptosis induction, and increased cell differentiation signaling. Recent epidemiologic studies demonstrate a reduction in non-Hodgkin lymphoma (NHL) risk with increased sunlight exposure. As sunlight is a major vitamin D source, it has been suggested that vitamin D status may mediate this observed association. This review provides a comprehensive discussion of the current epidemiologic evidence with regard to the investigation of an association between vitamin D status and NHL risk.