Social inequalities in breast cancer mortality among French women: disappearing educational disparities from 1968 to 1996

Abstract

We investigated the time trends in social inequalities in breast cancer mortality with an analysis by age at death and birth cohort using a representative 1% sample of the French population and four subcohorts (1968 -1974, 1975 -1981, 1982 -1988 and 1990 -1996). Causes of death were obtained by direct linkage with the French national death registry. Education was measured at the beginning of each period, and educational disparities in breast cancer mortality were studied among women aged 35 -74 at the beginning of each period. In the 1970s, higher breast cancer mortality was found among higher educated women. This positive association progressively weakened and no association remained in the 1990s although it disappeared earlier among younger women. In an analysis by birth cohort, the same pattern was found among women born before 1925, whereas no association between education and mortality was observed among women born after 1925. Educational disparities in breast cancer mortality are currently changing and the previously observed positive gradient has disappeared. An important question is whether these relations are indirect, and due to changes in the prevalence of risk factors associated with education, but which we could not study. (2006) Unlike most causes of death, breast cancer mortality risks have often been higher among women of high socioeconomic status (Faggiano et al, 1997;Heck et al, 1997;Dano et al, 2003Dano et al, , 2004. Some studies, however, found no such association (Lund and Jacobsen, 1991;Faggiano et al, 1997). Most breast cancer risk factors (reproductive behaviour, diet or physical activity) (Dos Santos Silva and Beral, 1997;Potter, 1997) as well as factors related to cancer survival (screening, treatment) (Auvinen and Karjalainen, 1997;Segnan, 1997) are associated with socioeconomic status and their distribution may have changed over time, producing in turn changes in social inequalities in breast cancer mortality. However, the few studies investigating time trends in social inequalities in breast cancer mortality have shown a decrease in socioeconomic disparities (Wagener and Schatzkin, 1994;Martikainen and Valkonen, 2000). British Journal of CancerWe have investigated the time trends in social inequalities in breast cancer mortality among women in France during the period 1968 -1996, with analyses by age at death and birth cohort. MATERIALS AND METHODSIn 1968, the French National Statistics Institute (INSEE) created a longitudinal population study (the 'permanent demographic sample' or EDP), which represented roughly 1% of the French population. The sample includes all persons born on one of four specific calendar dates every year, and is regularly updated to include new subjects with these birthdays (births and immigration). Data are updated at each successive census (1968, 1975, 1982 and 1990). The French National Statistics Institute supervises the keeping of vital records; so the vital status of EDP subjects is systematically monitored (Rouault, 1994). Causes of death were obtaine...

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