National impact of ICD-11 stroke reclassification on projected incidence across the United Kingdom.

The ICD-11 stroke definition expands stroke diagnosis by including neuroimaging-confirmed brain lesions regardless of symptom duration. Using directly age- and sex-standardized rates from the South London Stroke Register applied to UK Census 2021/2022 populations, we projected that ICD-11 to increase UK stroke incidence by ∼4.2%, yielding an estimated 2771 additional cases annually (England +2313; Scotland +241; Wales +142; Northern Ireland +75). Ethnicity-adjusted estimates suggested a 6.2% increase for England and Wales. These projections are scenario estimates that assume South London rates apply uniformly across the UK, their central limitation, and their realization will depend on local imaging and referral practice. Many additional cases will likely be managed in outpatient settings, requiring expanded provision, improved MRI, and strengthened cardiovascular prevention.