Background: The association between smoking and the risk of skin cancer has not been well established. Methods: In two large cohorts in the USA, we prospectively examined the risks of melanoma, basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) among participants grouped according to smoking variables. Results: Among men, compared with never smokers, ever smokers had a significantly lower risk of melanoma [relative risk (RR) = 0.72; 95% confidence interval (CI): 0.58-0.86]; those who smoked for 30 years had an RR of 0.65 (95% CI: 0.48-0.89) (Ptrend = 0.003); those who smoked 15 cigarettes per day had an RR of 0.32 (95% CI: 0.13-0.78) (Ptrend = 0.006) and those who smoked for > 45 pack years had an RR of 0.66 (95% CI: 0.45-0.97) (Ptrend = 0.03). Ever smokers also had a slightly lower risk of BCC (RR = 0.94; 95% CI: 0.90-0.98). There was no significant association for SCC (RR = 0.99; 95% CI: 0.89-1.12). In women, no significant association was found for melanoma (RR = 0.96; 95% CI: 0.83-1.10). Compared with never smokers, ever smokers had a slightly higher risk of BCC (RR = 1.06; 95% CI: 1.03-1.08) and a higher risk of SCC (RR = 1.19; 95% CI: 1.08-1.31). A significant inverse association between smoking and melanoma was limited to the head and neck (RR = 0.65; 95% CI: 0.42-0.89). Conclusions: Smoking was inversely associated with melanoma risk, especially on the head and neck. Further studies are warranted to investigate the underlying mechanism(s).
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