Malignant melanoma in England: risks associated with naevi, freckles, social class, hair colour, and sunburn

Abstract

In a case-control study in the Midlands of England, 195 subjects with superficial spreading or nodular melanoma were compared to age- and sex-matched controls chosen from all inpatients or outpatients in hospitals serving the defined source population. Significant increases in melanoma risk, after adjustment for other factors, were seen in association with total naevi on the arms (odds ratio (OR), for 15+ naevi compared to none = 3.8), intense freckling as an adult (OR = 6.2), and as a child (OR = 6.0), and higher social class (OR = 2.4). Positive single factor associations were also seen with light or red hair colour, tendency to sunburn easily, and a history of sunburn at ages 8-12, although these were not significant when adjusted for the other factors. No significant effect was seen with naevi greater than 6 mm, or with raised naevi, when adjusted for total number of naevi. Total arm naevi and density of freckling had independent effects, consistent with a multiplicative effect, the OR in those with 10+ naevi and heavy freckling being 20.8. The risk associated with red hair was independent of naevi, but associated with freckling. The strongest association with sunburn history was seen with a history of sunburn in childhood, with sunburn at later times, having smaller effects, or none. These results shows that freckling and social class as well as naevi are strong and independent risk indicators for melanoma. These associations were generally consistent by type of melanoma, sex, age, and extent of regular exposure of the body site affected, although the social class gradient was observed neither for nodular melanoma nor for melanomas occurring on the most exposed body sites.