Social inequality and incidence of and survival from breast cancer in a population-based study in Denmark, 1994–2003

Abstract

We investigated the effects of socioeconomic, demographic and health-related indicators on the incidence of and survival from breast cancer diagnosed in 1994–2003 with follow-up through 2006 in Denmark using information from nationwide population-based registers. The analyses were based on data on 25,855 patients with breast cancer in a cohort of 3.22 million people born between 1925 and 1973 and aged ⩾30 years. In general, the incidence of breast cancer increased with increasing social advantage, with unemployment or retirement, with increasing urbanicity and with being single or divorced. A history of admission for a psychiatric disorder increased the incidence of breast cancer. The overall relative short-term survival was high (96%), but survival improved with higher educational level and income. Whilst the relative 5-year survival after breast cancer was high (79%), there was significantly poorer relative survival amongst less advantaged and single women.

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.