Incidence and Time-Varying Risk of Post-Stroke Hydrocephalus: A National Cohort Study in South Korea

Background Hydrocephalus is a potentially serious complication of stroke that can lead to long-term neurological impairment. However, population-based evidence on its incidence and time-varying risk remains limited. Methods A retrospective cohort study was conducted using data from the Korean National Health Insurance Service–National Sample Cohort (2002–2013), including 16,514 patients newly diagnosed with hemorrhagic and ischemic stroke and 82,570 propensity score-matched controls. Stroke and hydrocephalus were defined based on codes set forth by the International Classification of Diseases, 10th Edition. Time-stratified Cox regression was applied owing to the violation of the assumption for proportional hazards. Results During a mean follow-up of 4.3 years, the incidence rate of hydrocephalus was 1.82 per 1,000 person-years in the stroke cohort, versus 0.11 in the controls (IRR, 17.11; 95% CI, 11.89–24.62). The adjusted hazard ratio (aHR) was highest within three years post-stroke (aHR, 29.53), declining over time but remaining elevated up to nine years. Patients with hemorrhagic stroke had a markedly higher early risk (aHR, 54.93), whereas those with ischemic stroke showed a delayed, biphasic risk pattern. Female and younger patients had higher relative risks despite lower absolute incidence. Risk was also elevated in association with smoking, alcohol use, high cholesterol, abnormal BMI, and higher income levels. Conclusion Stroke significantly increases the long-term risk of hydrocephalus, with distinct temporal patterns by stroke subtype. These findings emphasize the need for prolonged monitoring and individualized preventive strategies, especially for high-risk subgroups. Further research is warranted to refine risk prediction and guide post-stroke management.