Socioeconomic and healthcare supply statistical determinants of compliance to mammography screening programs: A multilevel analysis in Calvados, France

Background: Although the literature on factors associated with mammography screening is abundant, reasons for underparticipation remain unclear, most studies having focused exclusively on individual factors. This study aimed at investigating the ecological influence of socioeconomic status and healthcare supply on compliance to organized breast cancer screening programs, on an unbiased sample based on data from the entire target population within a French geographical area, Calvados (n = 98,822 women). Methods: Individual data on participation and aggregate data on healthcare supply and socioeconomic status, respectively obtained from the structure responsible for organizing screening and the French census, were analyzed simultaneously using a multilevel model. Results: Uptake was lower among the youngest (50–54 years) and the oldest (70–74 years) women, compared to the intermediate 55–69 year age-group, with respectively OR = 0.73 (95%CI: 0.64–0.83) and OR = 0.78 (95%CI: 0.67–0.91). Uptake fell with increasing level of deprivation, a difference in uptake probability being observed between the least deprived and the most deprived areas (OR = 0.71; 95%CI: 0.59–0.86). Neither radiologist- nor primary care physicians-to-100,000 inhabitants ratios were associated with participation. Conclusions: Multilevel analysis allows to detect areas of weak participation statistically linked to areas of strong deprivation. So, even with organized breast cancer screening giving screening free of charge for target women, ecological socioeconomic factors have a more significant impact on participation than healthcare supply. These results suggest that targeting populations, in accurate geographical areas where women are less likely to participate, as identified socially and geographically in this study, could be adopted to reduce disparities in screening.