Sunlight exposure, hat use, and squamous cell skin cancer on the head and neck.

Abstract

Sunlight is the environmental exposure most often associated with squamous cell cancer (SCC) of the skin. It can be difficult to quantify the sunlight exposure of the skin because of the different types of clothing that may be worn. The problem is simplified for studies of SCC on the skin of the head and neck, where a hat is the only type of clothing that needs to be considered. The purpose of the study was to determine the risk for SCC of sunlight exposure on the skin of the head and neck, and the protective effect, if any, associated with wearing a hat. A case-control study of squamous cell carcinoma of the skin was conducted amongst men in the province of Alberta, Canada. Analysis was restricted to only those cases where cancer occurred on the head or neck, and their age and sex matched controls. Ethnicity, non-sunexposed skin colour, and hair colour each significantly affected the SCC risk. An increased SCC risk was also associated with greater cumulative sunlight exposure and with sunburns experienced during the ages 5 to 15 years. The risk associated with sunlight exposure was significantly elevated in men who reported that they had always or usually worn a hat. As observed in previous studies, SCC on the skin of the head and neck is associated with host pigmentation, sunburns occurring in childhood, and sunlight exposure during adulthood. The risk observed for wearing a hat may be due to bias or confounding; however, hats remain an unproven means of protection against SCC on the skin of the head and neck.