Hydrocephalus is a neurological condition characterized by elevated intracranial pressure resulting from the abnormal accumulation of cerebrospinal fluid (CSF) within the ventricles or subarachnoid space due to impaired CSF circulation [[1], [2], [3], [4], [5]]. It is a serious disorder that often necessitates neurosurgical intervention. Although the estimated prevalence of pediatric hydrocephalus is approximately 88 per 100,000 individuals, the burden significantly increases with age, reaching 175 per 100,000 among older adults (≥65 years) and >400 per 100,000 in those aged ≥80 years [6]. In contrast, the prevalence among adults aged 18–64 years is estimated at approximately 11 per 100,000 [7]. These findings suggest that the overall global burden of hydrocephalus is substantially greater than previously estimated, particularly when adult and elderly populations are considered.

The socioeconomic impact of hydrocephalus is substantial in terms of medical costs, hospitalization rates, and long-term disability. For instance, in the United States, tens of thousands of hospitalizations associated with hydrocephalus occur each year, with annual hospital expenditures reaching several billion dollars. Furthermore, patients with hydrocephalus often experience lifelong neurological impairments. The high cost of treatment, frequent hospital admissions, and enduring disabilities highlight the considerable burden that hydrocephalus imposes on society. Therefore, identifying the underlying mechanisms and risk factors of hydrocephalus is essential for developing effective prevention and early intervention strategies.

Various conditions can lead to the development of hydrocephalus, including intraventricular hemorrhage, subarachnoid hemorrhage, infection, tumors, and congenital malformations [8]. Among these, head trauma is a major cause of hydrocephalus in adults [9]. It is estimated that approximately 2%–50% of all hydrocephalus cases are attributable to trauma [10]. Posttraumatic hydrocephalus (PTH) not only significantly impairs patients’ recovery and quality of life but also is closely associated with poor long-term outcomes [[1], [2], [3], [4], [5]]. Therefore, early prediction and appropriate management of PTH in patients with head trauma are crucial.

Most previous studies have been limited to single-center case series or populations with severe traumatic brain injury (TBI) [11]. The reported incidence rates (IRs) of PTH vary widely, ranging from 0.15% to 51.4% [4,[11], [12], [13], [14], [15], [16]], reflecting the lack of a clear and standardized definition of PTH [3,17]. Moreover, most studies have focused on the risk of developing PTH within 1 year after head trauma, and studies examining the long-term effects of head trauma on the development of hydrocephalus remain scarce [17]. However, hydrocephalus can develop several years after trauma, and short-term follow-up may underestimate its true incidence. Although previous studies have provided important preliminary data for identifying potential risk factors, large-scale population-based studies investigating risk factors are lacking, and the incidence of PTH in adults remains unclear.

To address this knowledge gap, this study investigated the incidence and risk factors of PTH using data from the Korean National Health Insurance Service (KNHIS). Furthermore, this study aimed to elucidate the temporal relationship between head trauma and the development of PTH using long-term follow-up data spanning 10 years after head trauma.