Cutaneous malignant melanoma in Norway: variation by region of residence before and after the age 17

Objective: The aim of this study was to examine indirectly the importance o f sun exposure during childhood and adolescence for the development of cuta neous malignant melanoma (CMM) by using a migration approach. Methods: A nested case-control study was carried out based on all inhabitan ts living in Norway at any time between 1960 and 1980. The cases were all d iagnosed between 1960 and 1992 (n = 13,934) and 10 controls were added for each case (n = 130,507). Analyses were conducted on residence history in th e southeast, mid-west and northern part of Norway, before and after age 17, also including working condition and educational level. Results: Birthplace in southeast was found to be twice as hazardous for the risk of CMM compared with birthplace in the north. The region of residence before as well as after age 17 was shown to influence the risk of CMM; the risk pattern in migrants tended to change direction toward the risk in the region to which they move. Associations was found between indoor working c ondition and CMM, and between high level of education and CMM, which suppor t the hypothesis that pattern of sun exposure in adulthood affects the risk of CMM. Conclusion: The results indicate sun exposure at any age to be of importanc e for the lifetime risk of CMM.