Objectives Sedentary behaviour (SB) is associated with increased risks of breast, colorectal, endometrial, ovarian and rectal cancers. However, the number of cancer cases attributable to SB in Germany and the associated costs are unknown.

Setting Numbers and proportions (population-attributable fractions, PAF) of new cancer cases attributable to SB with published risk estimates for Germany for the years 2024, 2030 and 2040.

Participants Sex-specific and age-specific population projections, national cancer incidence and exposure data. Primary and secondary outcome measures: new cancer cases attributable to SB and healthcare costs associated with cancer cases attributable to SB in Germany for the year 2024.

Results Estimated numbers of cancers attributable to SB are projected to be up to 7612 cases (6% of total cancer cases) in 2024, up to 7899 cases (6%) in 2030 and up to 8245 cases (6%) in 2040. The PAF attributable to SB in women is 3% for breast cancer, 8% for colon cancer, 9% for both endometrial and ovarian cancers and 2% for rectal cancer. In men, the PAF is 9% for colon cancer and 3% for rectal cancer. In 2024, the estimated costs of SB-attributable cancers are €270 million for colon cancer, €51 million for rectal cancer, €234 million for breast cancer and €242 million for female genital cancers.

Conclusions A considerable number of cancer cases can be attributed to SB, which also imposes a large health economic burden. Implementing effective prevention measures, such as workplace, school or commuting interventions, is needed to reduce the incidence of cancer attributable to this modifiable risk factor.