Non-melanoma skin cancer and solar keratoses II analytical results of the South Wales Skin Cancer Study.

This study aimed to identify risk markers for prevalent solar keratoses (SKs) and squamous cell carcinomata (SCC) combined, for incident SKs and for spontaneous remission of SKs and to evaluate primary preventative measures. It was a cross-sectional study, with follow-up, conducted in South Wales, and involved 1034 subjects aged 60 years and over. The main outcome measures were the presence of and changes in SKs, and presence of skin cancers, on sun-exposed skin, and risk factors for prevalent SKs/SCCs and for incidence and remission of SKs. We found that variables independently associated with prevalent SKs/SCCs were: age [80 + years vs 60-64 years, odds ratio (OR) 3.7]; sex (male vs female OR 2.2); cumulative sun exposure (top quintile vs bottom quintile OR 3.3) and skin type (skin type 1 vs 4 OR 12.4). Use of sunscreen or protective clothing was not protective after controlling for confounders. Males and those who sunbathe infrequently showed greater remission of SKs. Older subjects and those spending most time in the sun in the preceeding 2 years were most likely to develop new SKs. We conclude that the risk factors identified are consistent with results from sunnier countries. The failure of sunscreen or clothing to emerge as protective raises doubts as to whether these measures are as effective in routine use in the general population as theoretical considerations and the limited trial evidence would predict. Recently reported sun exposure appears to influence the risk of developing new SKs.