Down’s syndrome (DS) in France: a nationwide observational study on prevalence <65 years, mortality, comorbidities, and healthcare use in 2019 relative to non-DS individuals

Background: We investigated the mortality, social deprivation, comorbid conditions and healthcare use of Individual with Down’s syndrome (IDS) relative to the non-IDS general population. Methods: : We selected 98% of the 52.4 million people <65 years of age present in the national health data system for a cross-sectional study in 2019. IDS (35,342) were identified on the basis of an ICD-10 code (Q90) for hospital diagnosis or long-term disease (LTD) status qualifying for 100% reimbursement of healthcare. Risk ratios (RR) were calculated for the comparison of frequencies between the IDS and non-IDS groups. Results: The prevalence of IDS <65 years old was 0.07% (48% were female). Mortality was high for IDS (<65 years 4.6%, RR=10.2; <1 year 4.3%, RR=18.9). The proportion of IDS was higher in the most disadvantaged quintile of municipalities than for the least disadvantaged (<1 year: 0.08% vs. 0.05%). Comorbidities were most frequent among IDS (23.9% of those <1 year old had another LTD, RR=20.1). Tumors were diagnosed less frequently among IDS (1.2%, RR=0.7), except for myeloid leukemia (0.1%, RR=4.6), lymphoid leukemia (0.2%, RR=6.1) and testicular tumors (0.3%, RR=4.5). Dementia (1.2%, RR=28.7), mental retardation (4.7%, RR=20.7), epilepsy (4.2%, RR=9.1) and cardiac malformations (5.2%, RR=52.2, especially before the age of 4 years (16%), cardiac insufficiency (1.2%, RR=6.7) and valvular disease (0.9%, RR=5.8) were more frequent in IDS. Hospital admissions were more frequent among IDS for aspiration pneumonia (0.7%, RR=89.2), respiratory failure (0.4%, RR=16.9), sleep apnea at any age (1.1%, RR=8.3), cryptorchidism (0.3%, RR=5.9), iron deficiency (0.1%, RR=1.4), protein-energy malnutrition (0.1% RR=7.5), type 1 diabetes (0.2%, RR=2.8) and hypothyroidism (0.1%, RR=71.8). IDS were more likely to have had at least one visit to the emergency room (9.1%, RR=2.4), a short hospital stay (24.2%, RR=1.6), or home hospitalization (0.6%, RR=6). They were more likely to visit certain specialists,: ENT (22.1%, RR=3.0), cardiologist (17.2%, RR=2.6), neurologist (5.1%, RR=2.4), pediatrician (2.1%, RR=3.1) and thoracic surgeons (0.3% RR=1.9). Conclusions: : This study is the first detailed national study comparing IDS and non-IDS by age group, for comorbid conditions and healthcare use. These results could help to optimize counselling, prenatal healthcare and medical and social support.