Skin cancer screening in Okinawa, Japan

Depletion of the ozone layer has been observed on a global scale. Ozone dep letion increases the amount of biologically harmful solar ultraviolet radia tion (UV) that reaches the surface of the Earth, leading to an increased in cidence of skin cancer. We previously reported the prevalence and incidence of actinic keratosis (AK) in Kasai City, which is located almost at the ce nter of Japan. To evaluate the effects of different ambient annual UV doses on the prevalence and incidence of non-melanoma skin cancer and AK in Japa n, we screened for skin cancer on Ie Island in Okinawa at the southern end of Japan, where the annual cumulative dose of UV is assumed to be the highe st in Japan. The island had a population of 5562 in 1993. A prospective 4-y ear population-based study on the prevalence and incidence of cutaneous neo plasms was conducted by examining the sun-exposed skin of people over 40 ye ars of age living on Ie Island. In 1993-1996, 86 cases of AK, nine of basal cell carcinoma (BCC), and two of squamous cell carcinoma were identitied. The annual prevalence of AK on Ie Island was 1159.4 in 1993, 572.8 in 1994, 1014.3 in 1995 and 988.9 per 100000 Japanese in 1996. These values were si gnificantly higher than those in Kasai City. The annual age-adjusted odds r atios for AK of Ie Island to Kasai City were 2.79, 1.38, 2.45 and 2.39, res pectively. The incidences of AK On Ie Island per 100000 were 637.0 in 1995 and 625.5 in 1996, which were also significantly higher than those in Kasai City (223.6 in 1993 and 171.2 in 1994). The prevalence of BCC was 123.6 an d the incidence was 26.1. Together with our previous reports, the present r esults show a possible inverse relationship between the prevalence and inci dence of AK and latitude among Japanese people. (C) 1999 Elsevier Science I reland Ltd. All rights reserved.