High incidence and regression rates of solar keratoses in a queensland community

The presence of solar keratoses on the skin is one of the major risk factors for basal cell and squamous cell carcinomas, which constitute a growing public health problem in today's white populations. In spite of this, little is known of the natural history of solar keratoses. We conducted follow-up studies to monitor the incidence, regression, and recurrence rates of solar keratoses in a random sample (N = 96) of the Nambour community in Queensland. At baseline, 43 participants (46%) were diagnosed with at least one solar keratosis [26 men (55%), 17 women (37%)] with a total count of 494 prevalent solar keratoses. The distribution of lesions per person was highly skewed, with 11 individuals (12%) having 65% of the total number of solar keratoses. During 12 mo of follow-up, 614 incident solar keratoses were diagnosed (549 in men and 65 in women); 526 solar keratoses regressed and 53 prevalent solar keratoses recurred, giving a net 45% increase in solar keratosis numbers in men (from 354 to 512 solar keratoses) and a net 44% reduction in women (from 114 to 64). Regression rates were higher in prevalent (74%) than incident (29%) solar keratoses. Solar keratosis prevalence increased with age in both sexes, and individuals with solar keratoses at baseline were over seven times more likely to develop additional solar keratoses in the next 12 mo than those without prevalent solar keratoses at baseline. These results show that the natural history of solar keratoses in the community is one of high turnover and that a small percentage of susceptible individuals carry the major burden of solar keratoses in the community.