Factors influencing participation in breast cancer screening in an urban setting. A study of organized and individual opportunistic screening among potentially active and retired women in the city of Nice

•Over a 2-year period, 24,396 organized and opportunistic breast screening tests were conducted in an urban setting.•The social gradient was positively correlated with the participation.•Managerial status was negatively correlated with organised screening.•Single working women had a higher risk of non-participation.•Access to public transport facilitated participation.