Clinical characteristics and outcomes of intracerebral haemorrhage in young vs older adults: insights from the INTERACT3 trial

INTRODUCTION: ICH is a severe form of stroke with increasing global burden. Although more common in older adults, ICH in younger individuals (≤50 years) is a clinically distinct but understudied subgroup. This secondary analysis of the INTERACT3 trial compared baseline characteristics, management and outcomes between younger and older ICH patients. PATIENTS AND METHODS: INTERACT3 was a stepped-wedge, cluster-randomised trial conducted in 122 hospitals across 10 countries (2017-2021), evaluating a bundled care intervention for acute ICH. This sub-study analysed 7031 patients and compared demographics, imaging features, in-hospital treatment and 6-month outcomes between age groups. Primary outcomes were functional status (mRS), mortality and quality of life (EQ-5D-3L). Outcomes were analysed using generalised linear-mixed models accounting for clustering by hospital (random effect) and fixed effects for time period and cluster treatment assignment, with additional adjustment for pre-specified patient-level covariates. RESULTS: Of 7031 patients, 1351 (19.2%) were aged ≤ 50 years. Younger patients were more often male (70.8% vs 62.4%, P < .0001), had higher body mass index (BMI) (25.3 vs 23.8 kg/m2, P < .0001) and were more likely to smoke (36.1% vs 21.4%) and consume alcohol (33.2% vs 13.3%). Despite having slightly larger haematoma volumes (18.0 vs 15.0 mL, P < .0001), younger patients had significantly better outcomes, with lower 6-month mortality (9.1% vs 16.6%; adjusted OR 0.42; 95% CI, 0.33-0.54) and reduced rates of death or disability (46.5% vs 57.8%; OR 0.56; 95% CI, 0.48-0.65). A significant age-by-treatment interaction was observed (P = .0251). CONCLUSION: Younger ICH patients demonstrated a distinct risk profile and better recovery, and benefiting more from bundled care interventions. These findings highlight the importance of early, intensive management and tailored prevention strategies targeting modifiable lifestyle risks in younger populations.