Sunlight and non-Hodgkin's lymphoma: A population-based cohort study in Sweden

Indirect evidence, notably ecological comparisons and an association with s kin cancer, links non-Hodgkin's lymphoma (NHL) with exposure to sunlight. W e conducted a population-based, nationwide cohort study with exposure to ou tdoor work inferred from job titles reported in the population and housing censuses in 1960 and/or 1970 and by classifying each individual's work and home addresses according to latitude. Follow-up for cancer incidence was ac complished through record linkages with the virtually complete Swedish Canc er Registry. The cohort included all Swedish residents who were recorded as gainfully employed in both censuses. Altogether 4,171,175 individuals cont ributing 69,639,237 person-years accrued through 1989 were included in the analyses. We identified 10,381 cases of NHL, 4,018 cases of chronic lymphoc ytic leukemia(CLL), 11,398 cases of malignant melanoma (MM) and 11,913 case s of squamous cell skin cancer (SCC). We calculated age-adjusted relative r isks for NHL, CLL, MM and SCC in strata based on estimated residential and occupational sunlight exposure. Interaction effects were considered for pes ticide and solvent exposure. NHL, MM and SCC, but not CLL, were positively associated with increasingly southerly residential latitude, with stronger associations seen for skin cancer compared to NHL. Occupational sun exposur e was not associated with the risk of developing any of the studied cancers . Pesticides and solvents also were not related to an increased risk of NHL , nor did these exposures enhance effects of residential or occupational su nlight exposure. Our results provide some support for an association of sun light exposure with NHL incidence based on the associations seen using geog raphic latitude of residence as a proxy for exposure. Although type of occu pation may be an imperfect index of the biologically relevant ultraviolet ( UV) light dose, our data on individual exposure are not consistent with an important role of sunlight in the etiology of NHL. Int. J. Cancer 80:641-64 5, 1999. (C) 1999 Wiley-Liss, Inc.