Avoidable Mortality in Adults With Down Syndrome or With Other Intellectual Disabilities

Importance Down syndrome is the most common genetic cause of Alzheimer disease. Adults with Down syndrome experience higher mortality than the general population. However, the avoidable causes and their associated factors remain unclear. Objective To compare the proportion and causes of avoidable mortality in adults with Down syndrome, adults with other intellectual disabilities, and the general population, and to identify factors associated with avoidable death. Design, Setting, and Participants This population-based retrospective cohort study used data from the Learning From Lives and Deaths mortality review and the Office for National Statistics in England from 2016 to 2023. It included adults with Down syndrome (n = 3381), other adults with intellectual disabilities (n = 15 347), and the general population (n = 4 163 160). Exposures Down syndrome status, ethnicity, socioeconomic deprivation, co-occurring health conditions, COVID-19 pandemic period. Main outcomes and measures Proportion and causes of avoidable, treatable, and preventable deaths according to Organisation for Economic Co-operation and Development/Eurostat criteria; odds of avoidable death estimated using logistic regression; and age at avoidable death using Cox regression. Factors associated with avoidable death and age at death were also evaluated. Results Among 3381 adults with Down syndrome (1892 male [56.0%]; median [IQR] age at death, 59.5 [54.3-64.2] years), 1589 (47.0%) died from avoidable causes. Among 15 347 adults with other intellectual disabilities (8675 male [56.5%]; median [IQR] age at death, 63.8 [51.7-73.4] years), 6885 (44.9%) died from avoidable causes. Both proportions were substantially higher than in the general population (22.0%) (both P < .001). Treatable deaths were more common (972 [28.7%] vs 3847 [25.1%] vs 317 968 [7.6%]), with epilepsy and pneumonia as the leading treatable causes. Down syndrome was independently associated with higher odds of avoidable death (aOR, 1.15; 95% CI, 1.06-1.25) and earlier age at avoidable death (aHR, 1.49; 95% CI, 1.40-1.58). Minoritized ethnic background, asthma, diabetes, and osteoporosis were each independently associated with higher odds of avoidable death, and minoritized ethnic background and greater socioeconomic deprivation with earlier age at avoidable death. Conclusions and relevance In this cohort study of adults with Down syndrome and other adults with intellectual disabilities in England, avoidable mortality exceeded that of the general population. For the adults with Down syndrome, epilepsy and pneumonia were the dominant treatable causes. These findings support proactive integrated neurological care, including epilepsy review with dementia monitoring, pneumonia prevention, and respiratory vaccination, alongside targeted interventions for minoritized ethnic groups and socioeconomically deprived groups.