Cancer risk by education in Iceland; a census-based cohort study

Abstract

Earlier studies have shown that cancer risk is related to educational level in many countries. The relationship between education and cancer risk has not been studied in the small, but ethnically homogenous, Icelandic population postulated to be outstanding as regards social equity. Material and methods. We conducted a follow-up study of a cohort of 60 194 males and 58 505 females aged 20–64 at census 1981 in Iceland. Information on education from the census was classified into three educational groups and linked with the population-based Icelandic Cancer Registry. Standardized incidence ratios (SIRs) were calculated for the period 1982 to 2004. Results. We found a significant association between educational level and cancer risk. Among males with academic education, the SIR was elevated for prostate cancer (SIR=1.17, 95% CI 1.05–1.30) and melanoma (SIR=1.41, 95% CI 1.00–1.93) and lowered for cancers of the lung (SIR=0.72, 95% CI 0.59–0.87) and stomach (SIR=0.67, 95% CI 0.48–0.90). Women with academic education had an increased risk of breast cancer (SIR=1.19, 95% CI 1.07–1.33) and a decreased risk of lung cancer (SIR=0.49, 95% CI 0.36–0.65). Increasing educational level was associated with a lowered risk of cervical cancer (p trend=0.017). Discussion. The association between education and cancer incidence seen in this study resembles observations from other countries and probably reflects concordance between social status and certain risk factors for cancer. Our study confirms health-related socioeconomic differences in Iceland and must be taken into account when programmes for health promotion are planned.