Objective  

Sun exposure is the main cause of melanoma in populations of European origin. No previous study has examined the effect of sun exposure on risk of multiple primary melanomas compared with people who have one melanoma.

Methods  

We identified and enrolled 2,023 people with a first primary melanoma (controls) and 1,125 with multiple primary melanomas (cases) in seven centers in four countries, recorded their residential history to assign ambient UV and interviewed them about their sun exposure.

Results  

Risk of multiple primary melanomas increased significantly (P < 0.05) to OR = 2.10 for the highest exposure quarter of ambient UV irradiance at birth and 10 years of age, to OR = 1.38 for lifetime recreational sun exposure, to OR = 1.85 for beach and waterside activities, to OR = 1.57 for vacations in a sunnier climate, to OR = 1.50 for sunburns. Occupational sun exposure did not increase risk (OR = 1.03 for highest exposure). Recreational exposure at any age increased risk and appeared to add to risk from ambient UV in early life.

Conclusions  

People who have had a melanoma can expect to reduce their risk of a further melanoma by reducing recreational sun exposure whatever their age. The same is probably true for a person who has never had a melanoma.