Breast cancer screening attendance in two Swiss regions dominated by opportunistic or organized screening

Background: In Switzerland, the French-speaking region has an organized breast cancer (BC) screening program; in the German-speaking region, only opportunistic screening until recently had been offered. We evaluated factors associated with attendance to breast cancer screening in these two regions. Methods: We analyzed the data of 50-69 year-old women (n = 2769) from the Swiss Health Survey 2012. Factors of interest included education level, place of residence, nationality, marital status, smoking history, alcohol consumption, physical activity, diet, self-perceived health, history of chronic diseases and mental distress, visits to medical doctors and cervical and colorectal cancer screening. Outcome measures were dichotomized into <= 2 years since most recent mammography versus >2 years or never. Results: In the German-and French-speaking regions, mammography attendance within the last two years was 34.9 % and 77.8 %, respectively. In the French region, moderate alcohol consumption (adjusted OR 2.01, 95 % CI 1.28-3.15) increased screening attendance. Compared to those with no visit to a physician during the recent year, women in both regions with such visits attended statistically significantly more often BC screening (1-5 times vs. no visit: German (adjusted OR 3.96, 95 % CI 2.58-6.09); French: OR 7.25, 95 % CI 4.04-13.01). Non-attendance to cervical screening had a negative effect in both the German (adjusted OR 0.44, 95 % CI 0.25-0.79) and the French region (adjusted OR 0.57, 95 % CI 0.35-0.91). The same was true for colorectal cancer screening (German (adjusted OR 0.66, 95 % CI 0.52-0.84); French: OR 0.52, 95 % CI 0.33-0.83). No other factor was associated with BC screening and none of the tests of interaction comparing the two regions revealed statistically significant results. Conclusion: The effect of socio-demographic characteristics, lifestyle, health factors and screening behavior other than mammography on non-attendance to BC screening did not differ between the two regions with mainly opportunistic and organized screening, respectively, and did not explain the large differences in attendance between regions. Other potential explanations such as public promotion of attendance for BC screening, physicians' recommendations regarding mammography participation or women's beliefs should be further investigated.