BACKGROUND: Down syndrome is the most common genetic disorder, and the life expectancy of patients with Down syndrome has increased over the decades. However, the diseases and social problems experienced by patients with Down syndrome remain unknown in Japan. Therefore, we aimed to investigate the disease status of such patients admitted to acute care hospitals in Japan. METHODS: This observational study was conducted using the Diagnosis Procedure Combination data from 2016 to 2021 to evaluate routes of admission, principal diagnoses, comorbidity of dementia, orthopedic surgeries for limb fractures, and discharge destinations of patients with Down syndrome (International Classification of Diseases, Tenth Revision code: Q90). RESULTS: Overall, 26,195 individuals with Down syndrome were included, of whom 5195 were ≥20 years of age. As the age increased, the number of admissions from home decreased and that from nursing homes increased. Pneumonia was the most common principal diagnosis, with the incidence of aspiration pneumonia increasing in patients >
40 years of age. We observed an increase in the incidence of dementia and surgery for limb fractures after 40 years of age. The number of discharges to home decreased with increasing age, whereas that to nursing homes increased with increasing age. CONCLUSIONS: These results suggest that patients with Down syndrome are often hospitalized because of pneumonia and that the incidence of aspiration pneumonia, dementia, and limb fractures increases after 40 years of age. Therefore, a system to prevent pneumonia, especially aspiration pneumonia, and limb fractures in patients with Down syndrome is needed.