The reversed social gradient: Higher breast cancer mortality in the higher educated compared to lower educated. A comparison of 11 European populations during the 1990s
Introduction
Socioeconomic differences in breast cancer mortality are of interest for several reasons. Firstly, the cancer site by far most prevalent in adult women in both developed and developing countries is cancer of the breast.1 Secondly, breast cancer is the only major cause of death with a consistently positive social gradient, and this has been reported in several countries, including Brazil,2 Denmark,3, 4 Czech Republic,5 Finland,6 France,7 Italy,8, 9 Norway,10, 11 Spain,12, 13 Sweden14 and the USA.15, 16 It is suggested that this positive educational gradient is mainly because the higher educated are older at the time of first childbirth.4, 11 Thirdly, breast cancer survival is higher among higher educated women,17 and this is partly explained by stage at diagnosis,18 but possibly also by access to screening and other factors.
Comparison of breast cancer mortality by socioeconomic position (SEP) in different populations with similar follow-up times has been done in one previous study.19 For all populations together, a significant positive gradient in breast cancer by educational level was found for women younger than 75 years, but not for older women.
We used the same longitudinal data as Huisman et al.19 but extended the analysis in the following ways: First, we included two additional populations (Denmark and France). Second, we looked specifically at variations between countries in educational inequalities in breast cancer mortality. Third, we distinguished between women aged 30–49 years and 50–69 years, and between married and non-married women.
We hypothesised that lower educational level is associated with decreased breast cancer mortality across all European populations. However, we expect variations between age groups (reflecting cohort effects, with smaller inequalities in younger age groups) and between marital status groups (with smaller inequalities among non-married, where the role of birth history is strongly attenuated).
Section snippets
Materials and methods
We used mortality data from an international study,20 which obtained longitudinal data on mortality by educational level, marital position, and 5-year age groups for 11 European populations: Finland, Norway, Denmark, England and Wales, Belgium, France, Switzerland, Austria, Turin, Barcelona and Madrid. Participants were enumerated during censuses in the early 1990s and followed up for different periods (Table 1). Most data sets covered the entire national population, except France (data from
Results
Women in Denmark had the highest breast cancer mortality rate, followed by Turin, Belgium, and England and Wales (Table 1). The lowest rates were found in Finland, Madrid and Austria. In between were Norway, Switzerland, France and Barcelona.
The age-adjusted breast cancer mortality rates among women with low education were lower than the mortality rates among those with a middle or high educational level in all populations, except in Finland, France and Barcelona. In Finland there were no
Discussion
A positive relationship between breast cancer mortality and educational level was found in most of the 11 populations, but not in Finland, France and Barcelona. There was a tendency for the observed positive relationship to be less marked for younger women than for older women. Similar relationships were observed both among never- and ever-married women. Eliminating breast cancer mortality would give a greater gain in life expectancy for highly educated than for those with low education,
Conclusion
A positive relationship between breast cancer mortality and educational level (i.e. higher risks for higher educated women) was found in most of our studied European populations. However, there was a tendency for smaller inequalities in younger compared to older age cohorts. Our findings tend to support the theory that time of child-bearing is an important part of the observed socioeconomic gradient. Policies and programs to reduce breast cancer incidence and case-fatality should ensure that
Conflict of interest statement
None declared.
Acknowledgements
The project was in part funded by the European Commission, through the Eurocadet Project (from the commission of the European communities research directorate-general, Grant No. EUROCADET: SP23-CT-2005-006528), and through the European Union Fifth Framework Program on Quality of Life and Management of Living Resources a grant (Contract QLK6-CT-1999-02161). The construction of the Swiss National Cohort has been supported by the Swiss National Science Foundation, Grants Nos. 32-5884.98 and
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