Cancer incidence and diagnostic characteristics in people with intellectual disabilities in the Netherlands: a national registry-based cohort study.

Objective: People with intellectual disabilities (ID) face notable health disparities, also affecting cancer care. This study is among the first to use nationwide population and cancer registry databases to compare cancer incidence in the population with ID and the general population.

Methods and analysis: A population-based cohort study enrolled all Dutch adults (18+) with indicators of ID (N=187 149) and a 1:4 random general population sample without ID (N=760 907). All cancer diagnoses from 1 January 2015 until 31 December 2020 were collected from the national cancer registry to compare incidence and diagnostic details.

Results: Overall, fewer incident cancer cases were found among individuals with ID than without ID (51.0 vs 104.1/10 000 person-years; adjusted OR (adj.OR) 0.79 (0.76-0.81)), with cases occurring at younger ages and being diagnosed more often at a more advanced stage than in the general population. Key distinctions from the general population include reduced odds of skin cancer (adj.OR 0.39 (0.36-0.43)) and elevated odds of cancer of unknown primary (OR 1.60 (1.29-1.98)). The fewest cancer diagnoses occurred among those entitled to long-term ID care (adj.OR 0.63 (0.60-0.66)), with those living independently being at greater risk for cancers of digestive, respiratory and female genital organs.

Conclusion: Although the overall incidence of cancer in the population with ID appears lower than in the general population, significant variations exist across ID subgroups and cancer types. These differences indicate varying exposures, lower cancer awareness and barriers to healthcare for individuals with ID. Addressing these differences requires customised strategies for public health, long-term care and oncology care.