DOES INTERMITTENT SUN EXPOSURE CAUSE BASAL-CELL CARCINOMA - A CASE-CONTROL STUDY IN WESTERN-AUSTRALIA

Our report deals with the relationship of pattern and timing of sun ex posure to basal cell carcinoma (BCC) in a population-based case-contro l study conducted in Western Australia in 1988. The main measure of in termittent exposure was based on the amount of exposure on non-working days relative to that over the whole week. Outdoor recreational activ ities, holidays and sunburn were also considered to be markers of inte rmittent exposure. We observed a statistically significant increase in risk of BCC with increasing proportion of weekly sun exposure obtaine d at the weekend, especially in late teenage (OR 3.9, 95% CI 1.9-7.8 f or maximum intermittency of exposure), exposure of the site of skin ca ncer during holidays (OR = 1.9, 95% CI 1.1-3.1 for the highest exposur e quarter) and sunburn to the site (ORs of 1.8 for 3-10 and 1.5 for 11 + sunburns in a lifetime). Risk of BCC increased substantially with i ncreasing intermittency in poor tanners but not at all in good tanners . Our data suggest that a particular amount of sun exposure delivered in infrequent, probably intense increments will increase risk of BCC m ore than a similar dose delivered more continuously over the same tota l period of time. (C) 1995 Wiley-Liss, Inc.