Hematocrit and Stroke: A Forgotten and Neglected Link?
Stroke is considered among the most common causes of mortality and disability, leading to dramatic socioeconomic consequences. From a pathophysiologic perspective, enhanced blood viscosity due to increased hematocrit might be associated with stroke through impaired cerebral blood perfusion. This association has remained rather neglected during previous decades, but newly emerged as an epicenter of scientific interest due to the unexpected elevation of stroke rates with sodium-glucose cotransporter-2 inhibitors, a new class of hypoglycemic drugs with otherwise dramatic cardiovascular benefits. The purpose of this article is to review available data on the relation between stroke and hematocrit values. Data from large observational studies point toward an increased risk for stroke in individuals with elevated hematocrit. Data also suggest that the coexistence of increased hematocrit values and hypertension significantly enhance the risk of cerebrovascular events compared with each condition alone. Additionally, high hematocrit values seem related to worse survival outcomes in post-stroke patients. Collectively, the association between hematocrit and stroke seems to be strong and independent in high hematocrit values (>0.50) in both previously healthy individuals and post-stroke patients, but remains less clarified in patients with normal hematocrit values.