Colorectal Cancer Screening Among People With Intellectual Disabilities

Importance  
Colorectal cancer mortality is elevated among people with intellectual disabilities, potentially because of delayed diagnosis.

Objective  
To compare colorectal cancer screening participation and completion among people with and without intellectual disabilities.

Design, Setting, and Participants  
This nationwide, register-based cohort study was conducted in Denmark, where all residents aged 50 to 74 years are invited to biennial, free-of-charge colorectal cancer screening. People with and without intellectual disabilities born between 1940 and 1973 and invited to colorectal cancer screening at least once between 2014 and 2023 were included.

Exposure  
Intellectual disability, defined as being registered with an intellectual disability diagnosis or a diagnosis most likely leading to intellectual disability. Disability severity (mild, moderate, severe, and profound) was available for a subpopulation.

Main Outcomes and Measures  
The primary outcomes were colorectal cancer screening participation and completion, including stool sample return, screening results, and diagnostic examination (mainly colonoscopy) following a positive screening test result. The pseudo-observations method was used to estimate cumulative incidence differences and cumulative incidence ratios between people with and without intellectual disability.

Results  
The study included 17 117 people with (median [IQR] age, 55.2 [50.2 to 63.2] years; 8445 female [49.3%]) and 149 162 without (median [IQR] age, 54.8 [50.2 to 62.5] years; 75 324 female [50.5%]) intellectual disabilities. Among those, 5170 people with intellectual disabilities (30.2%) and 83 709 people without (56.1%) returned a stool sample within 90 days of first invitation (adjusted cumulative incidence difference, −23.2 percentage points; 95% CI, −24.0 to −22.4 percentage points), with participation increasing with disability severity (range, 1453 of 5293 individuals with mild [27.5%] to 198 of 488 individuals with profound [40.6%] intellectual disabilities). Nonanalyzable samples were more common among people with vs without intellectual disabilities (105 individuals [1.8%] vs 330 individuals [0.4%]). Among those with a positive screening test result, 347 people (70.5%) with intellectual disabilities and 4724 (90.2%) without underwent diagnostic examination (mainly colonoscopy) within 60 days (adjusted cumulative incidence difference, −17.9 percentage points; 95% CI, −22.1 to −13.7 percentage points). The proportion who underwent diagnostic examination decreased with increasing disability severity (range, 127 of 165 individuals with mild [77.0%] to 50 of 100 individuals with moderate to profound [50.0%] intellectual disabilities). Colonoscopies were more often incomplete among people with vs those without intellectual disabilities (109 individuals [28.2%] vs 673 individuals [13.8%]).

Conclusions and Relevance  
In this cohort study of people with and without intellectual disabilities, those with intellectual disabilities were less likely to participate in colorectal cancer screening and, when they did participate, more often encountered challenges with stool sample collection and colonoscopy completion. These disparities call for tailored, decision-supportive strategies to ensure equitable access to colorectal cancer screening.