Cancer-related mortality among people with intellectual disabilities: A nationwide population-based cohort study.

Background
Concerns have been raised about access to cancer screening and the timely receipt of cancer care for people with an intellectual disability (ID). However, knowledge about cancer mortality as a potential consequence of these disparities is still limited. This study, therefore, compared cancer-related mortality patterns between people with and without ID.

Methods
A historical cohort study (2015-2019) linked the Dutch adult population (approximately 12 million people with an ID prevalence of 1.45%) and mortality registries. Cancer-related mortality was identified by the underlying cause of death (according to the chapter on neoplasms in the International Classification of Diseases, Tenth Revision). Observed mortality and calculated age- and sex-standardized mortality ratios (SMRs) with 95% confidence intervals (CIs) were reported.

Results
There were 11,102 deaths in the ID population (21.7% cancer-related; n = 2408) and 730,405 deaths in the general population (31.2%; n = 228,120) available for analysis. Cancer was noted as the cause of death more often among people with ID in comparison with the general population (SMR, 1.48; 95% CI, 1.42-1.54), particularly in the young age groups. High-mortality cancers included cancers within the national screening program (SMRs, 1.43-1.94), digestive cancers (SMRs, 1.24-2.56), bladder cancer (SMR, 2.07; 95% CI, 1.61-2.54), and cancers of unknown primary (SMR, 2.48; 95% CI, 2.06-2.89).

Conclusions
Cancer was reported as the cause of death approximately 1.5 times more often in people with ID compared with the general population. This mortality disparity may indicate adverse effects from inequalities in screening and cancer care experienced by people with ID.

Lay summary
People with an intellectual disability (ID) may find it challenging to participate in cancer screening or to receive timely cancer care. To understand potential consequences in terms of mortality, this study compared cancer-related mortality between people with and without ID in the Netherlands. Cancer was reported as the cause of death approximately 1.5 times more often among people with ID than others. Because large differences were found that were related to screening cancers and cancers for which the primary tumor was unknown, this study's results raise concerns about equality in screening practices and cancer care for people with ID.