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There is inconsistent data on cancer risk in people with intellectual disability. Our primary objective was to compare the incidence of cancer in people with and without intellectual disability.

A cohort study using linked population-based administrative and cancer registry data in New South Wales, Australia 2001-2018. We compared the incidence of cancer in people with intellectual disability and a comparator group without intellectual disability matched for age, sex and residential postcode. We also compared cancer incidence in people with Down syndrome and people with intellectual disability without Down syndrome. We used a flexible parametric survival model accounting for competing risks.

People with intellectual disability had a slightly higher risk of developing any cancer (sub-hazard ratio, SHR 1.07 [95% CI 1.03 to 1.12]) compared to those without intellectual disability. An increased risk was evident in the 0-14 year (SHR 2.19, 95% CI 1.85 to 2.59) and 15-49 year (SHR 1.34, 95% CI 1.23 to 1.46) age groups, and a decreased risk was observed for those aged 50 years and above (SHR 0.93, 95% CI 0.88 to 0.98). People with intellectual disability had a higher risk of colorectal cancer (SHR 1.32, 95% CI 1.15 to 1.51) and a lower risk of prostate cancer (SHR 0.45, 95% CI 0.38 to 0.53) and melanoma (SHR 0.75, 95% CI 0.64 to 0.88). People with Down syndrome had a significantly higher risk of childhood cancer (SHR 7.94, 95% CI 5.72 to 11.04) compared to those with other intellectual disability, and a similar risk as an adult.

These findings underscore the need for targeted health promotion campaigns and, for adults, customised cancer screening programmes to improve access, acceptability and outcomes for people with intellectual disability.