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Original Investigation
March 10, 2008

Geographic Variation and Risk of Skin Cancer in US Women: Differences Between Melanoma, Squamous Cell Carcinoma, and Basal Cell Carcinoma

Author Affiliations

Author Affiliations: Channing Laboratory, Department of Medicine (Drs Qureshi, Laden, Colditz, and Hunter), and Department of Dermatology (Dr Qureshi), Brigham and Women's Hospital and Harvard Medical School, and Program in Molecular and Genetic Epidemiology (Dr Hunter), Department of Epidemiology (Drs Laden, Colditz, and Hunter), and Exposure, Epidemiology, and Risk Program, Department of Environmental Health (Dr Laden), Harvard School of Public Health, Boston, Massachusetts.

Arch Intern Med. 2008;168(5):501-507. doi:10.1001/archinte.168.5.501

Background  Occurrences of melanoma, squamous cell carcinoma (SCC), and basal cell carcinoma (BCC) have been associated with varying geography. Our goal was to evaluate differences in risk of these skin cancers according to residence at varying UV indices at 3 time points.

Methods  Prospective 1984-2002 study of 84 836 female nurses who lived in different UV index regions of the United States at birth and at 15 or 30 years of age. The outcome measure was diagnosis of melanoma, SCC, or BCC.

Results  During the 18-year study, 420 cases of melanoma, 863 cases of SCC, and 8215 cases of BCC occurred. At 30 years of age, age-adjusted risks for SCC were 1.47 (95% confidence interval [CI], 1.22-1.76) and 1.90 (95% CI, 1.51-2.36) for women residing in states with a UV index of 6 (medium) and 7 or more (high), respectively. Although elevated, the age-adjusted risk of BCC at 30 years of age associated with residence in these states was substantially less. Although the risk of melanoma was not elevated for women living in these states at 30 years of age, it was significantly elevated among women living in states with UV indices of 6 at birth and at 15 years of age. There was no material change in risk estimates with multivariate adjustment. For women who reported living in states with UV indices of 7 or more at all 3 time points, the multivariate risk of SCC was highest.

Conclusions  The risk of SCC is independently affected by residence in locations with medium and high UV indices; the gradient of risk is weaker for BCC; and the risk of melanoma does not change significantly across this gradient.