Prevalence of actinic keratosis in Japan.

Most of the epidemiological studies on skin cancer that have been conducted to date have addressed the incidence in light-skinned Caucasians. To determine the prevalence rate of skin cancer and actinic keratosis (AK) on sun-exposed body sites of Japanese in Japan, we examined the skin of 4736 people during health examinations. The study was undertaken in Kasai City, Japan, which had a population of 52,837 in 1992, where participants in a regional health examination were seen by dermatologists. The final diagnosis was made histopathologically. Participants were also interviewed by means of a questionnaire. A total of 36 cases of AK and two of basal cell carcinoma were identified, to give a prevalence of 413.4 per 100,000 for AK. The prevalence among outdoor workers was significantly higher than that of indoor workers. Furthermore, when the participants were classified into three Japanese skin types, the prevalence of AK among people of skin Type I, who are sensitive to UV irradiation, was significantly higher than that among people of skin Types II and III, who are less sensitive.