Impact of Physician Volume and Specialty on In-Hospital Mortality of Ischemic and Hemorrhagic Stroke

Background: The degree of association between mortality and case volume/physician volume is well known for many surgical procedures and medical conditions. However, the link between physician volume and death rate in patients hospitalized for stroke remains unclear. This study analyzed the correlation between in-hospital stroke mortality and physician volume per hospital, considering board certification status. Methods and Results: For this retrospective registry-based cohort study, data were obtained from the Japanese nationwide registry on patients hospitalized for ischemic stroke, intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH) between 2010 and 2016. The number of stroke care physicians and relevant board-certified physicians was also obtained. Odd ratios (ORs) of 30-day in-hospital mortality were estimated after adjusting for institutional and patient differences using generalized mixed logistic regression. From 295,150 (ischemic stroke), 98,657 (ICH), and 36,174 (SAH) patients, 30-day in-hospital mortality rates were 4.4%, 16.0%, and 26.6%, respectively. There was a correlation between case volume and physician volume. A higher number of stroke care physicians was associated with a reduction in 30-day mortality after adjusting for stroke case volume and comorbidities for all stroke types (all P for trend<0.05). Conclusions: An increased number of stroke care physicians was associated with reduced in-hospital mortality for all types of stroke. The volume threshold of board-certified physicians depends on the specialty and stroke type.