Colorectal cancer (CRC) incurs a significant disease burden globally. Organised CRC screening programmes have been widely implemented for early detection and prevention. To understand the public health impact of these programmes, quantitative evidence of changes in overall and age-specific population incidences is fundamental. We aimed to provide such evidence by exploiting a time lag in the implementation of organised screening in Sweden: two out of 21 regions (these two regions comprise nearly 20% of the total Swedish population) have offered organised screening since 2008; the other regions have offered CRC screening since 2021. Using registry data on diagnosed CRC cases and socio-demographics for all regions in Sweden over the period 1970–2019, Bayesian structural time series modelling and difference-in-differences were applied to analyse the impact of screening on age-specific population incidences over time (CRC cases per 100.000 persons/year). After inviting birth-year cohorts aged 60–69 years for stool-based testing, the incidence rate in the 70–74-year age group decreased significantly over time, with an average reduction of − 44·40 (95% CI − 58·15 to − 31·31) from 2011 to 2019 in the intervention regions. In the overall population aged 60–74 years, there was a net incidence decrease of − 7·99 (95% CI − 13·85 to − 2·39) since the initiation of organised screening in the intervention regions (2008–2019). Organised CRC screening for 60–69-year-olds generated a change in age-specific incidence patterns with a long-lasting incidence decrease in the 70–74-year-old population, implying reductions in the excess mortality and burden of the disease.

结直肠癌（CRC）在全球范围内造成了巨大的疾病负担。有组织的结直肠癌筛查计划已广泛实施，以实现早期发现和预防。要了解这些计划对公共卫生的影响，总体和特定年龄人口发病率变化的定量证据至关重要。我们的目的是利用瑞典实施有组织筛查的时间滞后来提供此类证据：自 2008 年以来，21 个地区中有两个地区（这两个地区占瑞典总人口的近 20%）提供了有组织的筛查；其他地区自 2021 年起提供了 CRC 筛查。利用 1970 年至 2019 年期间瑞典所有地区诊断的 CRC 病例和社会人口统计数据，应用贝叶斯结构时间序列模型和双重差分来分析影响随着时间的推移对特定年龄人群发病率的筛查（每 10 万人/年的 CRC 病例）。在邀请60-69岁的出生年份队列进行粪便检测后，70-74岁年龄组的发病率随着时间的推移显着下降，平均下降了− 44·40 (95% CI − 58· 15 至 − 31·31) 2011 年至 2019 年干预地区。自干预地区开始有组织的筛查以来（2008-2019年），60-74岁的总体人口中，发病率净下降了− 7·99（95% CI − 13·85至− 2·39） 。对 60-69 岁人群进行的有组织的 CRC 筛查改变了特定年龄发病率模式，70-74 岁人群的发病率持续下降，这意味着超额死亡率和疾病负担的减少。