SOLAR-RADIATION, LIP PROTECTION, AND LIP CANCER RISK IN LOS-ANGELES-COUNTY WOMEN (CALIFORNIA, UNITED-STATES)

A population-based case-control study of 74 women with lip cancer diag nosed from 1978 to 1985 in Los Angeles County (California, United Stat es) and frequency matched to 105 controls investigated the risk of sol ar radiation and protection from lip sunscreening agents to explore th e hypothesis that excess incidence of lip cancer seen in men is due pa rtly to lower rates in women, conferred by frequent use of lip protect ion. We confirm the importance in women of risk factors similar to tho se found in men, i.e., fair complexion, sun exposure, and smoking. Ris k was related strongly to lifetime solar radiation (odds ratio [OR] = 13.5 for highest quartile of exposure, 95 percent confidence interval [CI] = 4.5-40.6, P trend < 0.0001) and time spent outdoors (OR = 4.7 f or highest quartile of average yearly hours, CI = 1.9-12.1, P trend = 0.01). Further, among women with high lifetime solar-radiation exposur e, those who used lip protection once a day or less had twice the risk of lip cancer than women who used lip protection more than once a day (OR = 7.3, CI = 1.9-27.2 cf OR = 3.2, CI = 1.1-9.2). These findings s how that solar radiation is a major risk factor for lip cancer and sug gest that lip sunscreening is protective,thereby supporting the hypoth esis that use of lipstick and other sunscreening agents by women has c ontributed to their lower incidence of this disease.