Incidence of actinic keratosis of Japanese in Kasai City, Hyogo.

We determined the incidence of actinic keratosis (AK) among Japanese by screening for skin cancer in Kasai City, Hyogo, Japan, between 1993 and 1995. The incidence per 100,000 Japanese residents was 223.6 in 1993 and 171.2 in 1994. The prevalence of AK was 291.2 per 100,000 residents in 1993, 203.7 in 1994, and 86.8 in 1995. The prevalence in people who had more than six seborrheic keratoses on sun-exposed body sites and in people who had experienced severe sunburns with blister formation during childhood were significantly higher. These results indicate that more than six seborrheic keratoses and several episodes of blister formation in childhood may be risk factors for AK in the Japanese.