A pooled analysis of 10 case-control studies of melanoma and oral contraceptive use.

Data regarding the effects of oral contraceptive use on women's risk of melanoma have been difficult to resolve. We undertook a pooled analysis of all case-control studies of melanoma in women completed as of July 1994 for which electronic data were available on oral contraceptive use along with other melanoma risk factors such as hair colour, sun sensitivity, family history of melanoma and sun exposure. Using the original data from each investigation (a total of 2391 cases and 3199 controls), we combined the study-specific odds ratios and standard errors to obtain a pooled estimate that incorporates inter-study heterogeneity. Overall, we observed no excess risk associated with oral contraceptive use for 1 year or longer compared to never use or use for less than 1 year (pooled odds ratio (pOR)=0.86; 95% CI=0.74-1.01), and there was no evidence of heterogeneity between studies. We found no relation between melanoma incidence and duration of oral contraceptive use, age began, year of use, years since first use or last use, or specifically current oral contraceptive use. In aggregate, our findings do not suggest a major role of oral contraceptive use on women's risk of melanoma.

Case-control study of malignant melanoma in Washington State. I. Constitutional factors and sun exposure.

Constitutional factors and sun exposure were examined among 256 cases of melanoma and 273 controls in three counties of western Washington State. Cases were individuals diagnosed with melanoma at ages 25-65 years during 1984-1987 who were identified from a Seattle-Puget Sound cancer registry. Population controls were identified through random digit dialing and were randomly selected, stratified by age, sex, and county. Participants completed a telephone interview with questions on demographic, sun exposure, and constitutional factors. Risk factors for melanoma were examined through the use of logistic regression, controlling for age, sex, and educational level, and data on each exposure variable were tested for the significance of trends across levels of exposure. The constitutional factor most strongly associated with melanoma risk was sun sensitivity, measured as either reaction to chronic sun exposure (for no tan vs. deep tan, odds ratio (OR) = 9.0, 95% confidence interval (CI) 3.8-21.1; p < 0.001 for trend across four categories) or reaction to acute sun exposure (for severe burn vs. tan, OR = 5.7, 95% CI 2.6-12.6; p < 0.001 for trend across four categories). The number of raised nevi counted on both arms by subjects was also associated with increasing risk (for > or = 10 nevi vs. none, OR = 5.7, 95% CI 2.2-14.6; p for trend < 0.001). Sun exposure in adulthood and occupational sun exposure were not related to melanoma risk. The effect of sun exposure in childhood on melanoma risk was modified by tanning ability. Poor tanners showed no effect of sun exposure at ages 2-10 years or ages 11-20 years. In contrast, people who reported a deep or moderate tan in reaction to chronic sun exposure appeared to be protected from melanoma with increasing sun exposure at ages 2-10 years (for upper third vs. lower third, OR = 0.3, 95% CI 0.2-0.6; p for trend < 0.001), with identical results for exposure at ages 11-20 years. The finding that childhood sun exposure is protective only among those able to tan supports the hypothesis that developing a tan during childhood may reduce the risk of melanoma by offering protection from the effects of sunlight exposure.

Case-control study of malignant melanoma in Washington State. II. Diet, alcohol, and obesity.

Intakes of vitamin A, dietary antioxidants, and other dietary components were examined for their relation to the risk of malignant melanoma among 234 cases and 248 controls in three counties of western Washington State. Cases were drawn from persons diagnosed with melanoma between 1984 and 1987 and identified through a Seattle-Puget Sound cancer registry. Population controls were identified through random digit dialing and were randomly selected, stratified by age, sex, and county. Subjects completed a telephone interview and a mailed food frequency questionnaire asking for information on diet, demographic factors, and factors known to be associated with melanoma. Subjects were asked to estimate their food intake 7 years prior to diagnosis for cases and during a comparable time period for controls. Among data on 16 nutrients calculated from reported food intake, one significant finding emerged: Vitamin E obtained from food was inversely related to risk of melanoma (for highest quartile vs. lowest quartile, age-, education-, and energy intake-adjusted odds ratio (OR) = 0.34, 95% confidence interval (CI) 0.16-0.72; p for trend = 0.01). When intake of nutrients from food plus vitamin and mineral supplements was considered, zinc from food and supplements was associated with a decreased risk of melanoma (for highest quartile vs. lowest quartile, adjusted OR = 0.46, 95% CI 0.24-0.91; p for trend = 0.01). There was no evidence that vitamin A, preformed retinol, or carotenoids were associated with a decreased risk of melanoma or that alcohol or polyunsaturated fats were associated with an increased risk. Body mass index (weight (kg)/height (m)2) was significantly related to melanoma risk; cases were more obese than controls (for highest quartile vs. lowest quartile, age-, sex-, and education-adjusted OR = 1.90, 95% CI 1.10-3.27; p for trend = 0.02). These results provide limited support for the hypothesis that antioxidants such as vitamin E or cofactors in protection from oxidative damage such as zinc may be protective for melanoma, and they suggest that obesity should be measured in future studies of melanoma.

Melanoma risk by age and socio-economic status.

To explore the relationship between melanoma incidence, socio-economic status (SES), and site of occurrence, 1,804 cases of melanoma in Washington State from 1974-85 were analyzed by mean income of census tract of residence. (Census tracts are geographic divisions of state counties for which demographic information is provided by state agencies.) For males aged 30-69, as expected, the risk increased with income. Unexpectedly, at age 70 and over the trend was reversed (the heterogeneity of the age relationship was unlikely to be due to chance). In the older men, the increase with low income was found in the cases reported as Hutchinson's melanotic freckle and those which were not, being statistically significant in the latter. These findings suggest a role for long-continued sun exposure in the etiology of malignant melanoma.