A case-control study of malignant melanoma in Israeli kibbutzim

Background: Incidence rates for malignant melanoma in Israel are rising steadily, and the kibbutz population is at increased risk for this malignancy. Objectives: To assess the risk factors for malignant melanoma among kibbutz members compared to matched healthy controls. Methods: We conducted a case-control study of 168 malignant melanoma patients and 325 healthy controls, matched by age and gender. Data were collected on three categories of risk: demographic, personal (e.g., skin, eye and hair color), and environmental/behavioral (e.g., sun exposure, use of sunscreens). Results: There were no differences between the groups regarding sociodemographic data. Significantly more patients than controls had fair, vulnerable skin (P<0.001), light eyes (P<0.05), and fair hair (P<0.001). There was no difference in family history of malignant melanoma or other cancers. Patients with malignant melanoma had significantly more additional skin lesions (e.g., keratoses) (P<0.001). More patients than controls recalled having been exposed to the sun for long periods when they were 6-13 years of age. A conditional logistic regression analysis showed that fair hair, fair vulnerable skin, and additional skin lesions were independently associated with malignant melanoma (P<0.01). Conclusions: The main target population for interventions to reduce the incidence of malignant melanoma among kibbutz members should be individuals with these risk factors. A history of increased exposure to the sun from age 6 to 13 should also be taken into account as an independent risk factor.