["Journal of Applied Research in Intellectual Disabilities, Volume 39, Issue 3, May 2026. ", "\nABSTRACT\n\nBackground\nTo describe immediate and underlying causes of mortality (using ICD‐10 codes) and survival rates of aging adults with Down syndrome (Ds).\n\n\nMethod\nThis secondary analysis used the Healthy Aging and Intellectual Disabilities cohort. Adults with Ds (n = 149, ≥ 50 years at baseline) were matched 1:1 to adults with intellectual disabilities without Ds on age, sex and level of intellectual disability. Follow‐up was ~10 years post‐baseline, or at death.\n\n\nResults\nThe most common immediate and underlying causes of death in adults with Ds were respiratory diseases/infections, followed by cardiovascular disease and neuropsychiatric conditions. Unknown causes accounted for 29%–50% of deaths. Adults with Ds had higher mortality than matched comparators (HR = 5.05, 95% CI 3.10–7.47), increasing significantly with each year of age (HR = 1.08/year, 95% CI 1.04–1.11).\n\n\nConclusion\nRespiratory diseases, cardiovascular and neuropsychiatric conditions are important contributors to mortality in older adults with Ds, but large numbers of missing causes warrant cautious interpretation.\n\n"]