A PROSPECTIVE-STUDY OF INCIDENT SQUAMOUS-CELL CARCINOMA OF THE SKIN IN THE NURSES HEALTH STUDY

Background: Few epidemiologic studies are available that quantify the magnitude of the risk of squamous cell carcinoma (SCC) of the skin ass ociated with sun exposure and related factors such as skin type, In ad dition, several studies have found an association between cigarette sm oking and SCC, Purpose: We prospectively examined the risk of developi ng SCC in relation to phenotype and the effects of sun exposure, as we ll as to cigarette smoking and other factors, during 8 years of follow -up in a cohort of 107 900 predominantly white women aged 30-55 years at base line in 1976, Methods: Questionnaires regarding medical histor y and health-related variables were sent to Nurses' Health Study parti cipants every 2 years, beginning in 1976, Information on constitutiona l factors (natural hair color, childhood and adolescent tendency to su nburn and tan, and lifetime number of severe sunburns), lifestyle fact ors (regular time spent outdoors in the summer and sunscreen use), the state lived in at birth and at ages 15 and 30 years, and cigarette sm oking habits were ascertained by questionnaire, A total of 197 women w ith first-incident, histologically confirmed, invasive SCCs that were diagnosed from 1982 to 1990 were included in this analysis, Multivaria te analysis using proportional hazards models was used to calculate th e relative risks (RRs) and corresponding 95% confidence intervals (CIs ), with adjustment for confounders, Results: The risk of SCC was incre ased in women living in California (RR = 1.8; 95% CI = 1.3-2.6) and Fl orida (RR = 2.1; 95% CI = 1.1-3.9) at base line, compared with those l iving in the northeastern states, This risk was higher for women livin g in those states at birth and at 15 years of age (RR = 2.5; 95% CI = 1.4-4.4 for California and RR = 3.0; 95% CI = 0.7-1.2 for Florida), Re d (RR = 2.0; 95% CI = 1.1-3.7) and light brown (RR = 1.7; 95% CI = 1.2 -2.4) hair colors were associated with an increased risk of SCC, compa red with dark brown hair, After adjusting for the number of sunburns, women who tended to burn after 2 or more hours of sun exposure as chil dren had a slightly higher risk of SCC than those who never burned (RR = 1.5; 95% CI = 0.9-2.5 for burn and RR = 1.1; 95% CI = 0.6-2.0 for p ainful burn), although the actual number of severe burns appeared to b e a more important factor (RR = 2.4; 95% CI = 1.5-4.0 for six or more burns), Finally, current cigarette smokers showed a 50% increase in th e risk of SCC compared with never smokers (RR = 1.5; 95% CI = 1.1-2.1) , Conclusion: Exposure to the sun leading to sunburn, particularly at early ages, should be avoided to decrease the risk of incident SCC.