Social inequality and incidence of and survival from breast cancer in a population-based study in Denmark, 1994–2003
Introduction
In Denmark, the incidence of breast cancer has increased throughout the past few decades and, in 2003, when breast cancer was diagnosed in 3866 women, it became the most frequent cancer in women and the second commonest cause of death from cancer in Danish women.1 Several studies have indicated a positive association between high socioeconomic position and risk for breast cancer.2, 3, 4, 5, 6 This positive association can be explained partly by known risk factors, such as high age at first childbirth and few children,5 any use of oral contraceptives and hormone replacement therapy,5 high alcohol intake7 and living in an urban area.3 Whilst the risk for breast cancer increases with increasing socioeconomic position, socially deprived women have poorer survival from the disease.8, 9, 10, 11 This inverse association between socioeconomic position and the risk for dying from breast cancer might be due to more advanced stage at the time of diagnosis,8, 9, 11 a larger number of comorbid conditions,12 suboptimal treatment6 and less use of mammographic screening.
The aim of this study was to identify the effects of socioeconomic position and demographic and health-related indicators on the incidence of and survival from breast cancer in Denmark on the basis of information from the nationwide Danish administrative registers. It was carried out as part of a comprehensive, rigorous analysis of the role of socioeconomic position in cancer incidence and survival.
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Material and methods
The material and methods are described elsewhere.13 Briefly, the study population comprised all 3.22 million Danish residents (1.59 million women) born between 1925 and 1973 without a previous history of cancer and who entered the cohort at age 30 (see Fig. 1 in [13]). Information on socioeconomic, demographic and health-related indicators was obtained from various Danish registers based on the administrative data.13 Crude, age-specific and age-standardised incidence rates are presented for
Results
Breast cancer was diagnosed in 25,855 women, who formed the cohort study during the period 1994–2003, representing 72% of the cases of breast cancer diagnosed in Denmark in that period. Amongst Danish persons, the age- and period-standardised incidence rate was 195 per 100,000 person-years.
Discussion
In this population- and register-based cohort study, the incidence of breast cancer increased with higher socioeconomic position, in accordance with the results of other studies.2, 3, 6, 8, 9, 10, 11 In addition, after adjustment for education and disposable income, women living in the capital area, single women and women with a previous diagnosis of depression or schizophrenia had significantly higher risks for breast cancer than married women and women without psychiatric disorders. The risk
Conflict of interest statement
None declared.
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