Incidence and Mortality of Chronic Subdural Hematomas: A Population-Based Study

BACKGROUND: Despite a rising public health burden, there have been few population-based studies of chronic subdural hematomas (cSDH) in the United States. We provide the first estimates of cSDH incidence and mortality in a large, representative U.S. population. METHODS: In a representative 5-county region of Southern Ohio and Northern Kentucky, all adults with cSDH in 2019 and 2020 were identified and adjudicated by study physicians. Incidence rates were estimated and standardized to the US population based on age, sex, and race; 30-day and 1-year mortality rates were also estimated. The cause of death was determined using the National Death Index. RESULTS: A total of 353 patients with cSDH were identified. The median age was 76 (IQR, 65–85), 231 were men (65.4%), and 78 were Black (22.1%). Clinical frailty was prevalent among patients (the median retrospective score on the clinical frailty scale was 4), and only 128 (36.3%) were functionally unimpaired at baseline. The regional incidence rate was 16.3 cases/100 000 persons/y (95% CI, 13.9–19.0). Incidence was age- and sex-dependent, with men 85 and older having an incidence rate of 354.8 cases/100 000 persons/y (95% CI, 242.7–500.9). When adjusted to national demographics, the estimated overall US incidence rate was 17.3 cases/100 000 persons/y (95% CI, 14.7–19.9). The 30-day mortality rate after cSDH was 9.4% (95% CI, 6.5–12.9), and the 1-year mortality rate was 32.9% (28.0–38.0). Early mortality (≤30 days) was often partly or fully attributed to the cSDH (48.4% versus 16.1%; P =0.0004), whereas the most common causes of later mortality were neurodegenerative and cardiovascular diseases (27.2% and 28.4%, respectively). CONCLUSIONS: Our contemporary population-level data show that cSDH is common in the US and primarily afflicts patients with a high degree of functional impairment and frailty. While short-term mortality is low, longer-term mortality is high and often related to comorbid illnesses.