Cancer incidence among people with intellectual disability: a nationwide population-based cohort study in Denmark

People with intellectual disability have lower screening participation and higher cancer-related mortality, yet few studies have investigated cancer incidence in this group.

This study aimed to examine cancer incidence among people with intellectual disability compared to the general population.

In this Danish population-based cohort study, we identified people with intellectual disability and a 1:10 age- and sex-matched reference cohort. Using national register data, we calculated standardized incidence rates (SIR) adjusted for age and sex for any cancer and for site-specific cancers. We also assessed stage at diagnosis.

We identified 84,007 people with intellectual disability and 841,583 references, of whom 6701 and 87,955 had an incident cancer between 1978 and 2024. Cancer incidence was markedly elevated among children with intellectual disability (0-17 years; SIR: 4.55, 95% confidence interval [CI]: 4.12-5.00), modestly elevated among adults aged 18-59 years (SIR: 1.20, 95% CI: 1.16-1.25), and reduced among those aged ≥60 years (SIR: 0.87, 95% CI: 0.84-0.90). Cancer incidence was slightly elevated among people with mild (SIR: 1.05, 95% CI: 1.03-1.08) or unknown severity of intellectual disability (SIR: 1.09, 95% CI: 1.05-1.13), and reduced for those with moderate, severe, or profound intellectual disability. Variations were observed across cancer sites. Individuals with intellectual disability were more likely to be diagnosed with advanced (Odds Ratio [OR]: 1.28, 95% CI: 1.20-1.36) or unknown cancer stage (OR: 1.57, 95% CI: 1.46-1.69).

These findings underscore the need for cancer prevention and early detection, particularly among younger people and those with mild intellectual disability.