High and low hematocrit (Hct) and hemoglobin (Hb) levels are associated with the risk of cardiovascular disease. The purpose of this study was to determine the relationships of Hct, Hb and red blood cells (RBCs) with vascular function and structure. We measured flow-mediated vasodilation (FMD), nitroglycerin-induced vasodilation (NID), brachial intima media thickness (IMT), and brachial-ankle pulse wave velocity (baPWV) in 807 men. The subjects were divided into six groups according to the levels of Hct, Hb and RBCs. NID was highest in the 46.0–48.9% Hct group among the six groups according to Hct levels. Brachial IMT was lowest in the 46.0–48.9% Hct group among the six groups. There were no significant differences in FMD and baPWV among the six groups. We used 46.0–48.9% Hct as a reference to define the lower tertile. The adjusted odds ratio of being in the low tertile of NID was significantly higher in the < 42.9% and ≥ 49.0% Hct groups. Adjusted odds ratio of being in the low tertile of brachial IMT was significantly lower in the < 39.9% Hct groups. Similar results were obtained for Hb and RBCs. Low and high levels of Hct, Hb and RBCs were associated with vascular smooth muscle dysfunction, and low Hct levels were associated with abnormal vascular structure. Increases in the levels of Hct, Hb and RBCs within normal ranges may have beneficial effects on the vasculature.

血细胞比容（Hct）和血红蛋白（Hb）的高低与心血管疾病的风险有关。这项研究的目的是确定Hct，Hb和红细胞（RBC）与血管功能和结构的关系。我们测量了807名男性的血流介导的血管舒张（FMD），硝酸甘油诱导的血管舒张（NID），肱内膜中膜厚度（IMT）和臂踝脉搏波速度（baPWV）。根据Hct，Hb和RBC的水平将受试者分为六组。根据Hct水平，六组中Hct组的NID最高，为46.0-48.9％。在六组中，肱IMT在46.0％至48.9％Hct组中最低。六组之间的FMD和baPWV没有显着差异。我们使用46.0–48.9％Hct作为参考来定义较低的三分位数。在<42.9％和≥49.0％的Hct组中，处于NID低三分位数的调整后的优势比显着更高。在<39.9％Hct组中，臂内IMT处于低三分位数的调整后的优势比显着降低。Hb和RBC的结果相似。Hct，Hb和RBC的低和高水平与血管平滑肌功能障碍有关，而Hct的低水平与血管结构异常有关。正常范围内Hct，Hb和RBC的水平升高可能会对脉管系统产生有益影响。血红蛋白和红细胞与血管平滑肌功能障碍有关，而低血红蛋白水平与血管结构异常有关。正常范围内Hct，Hb和RBC的水平升高可能会对脉管系统产生有益影响。血红蛋白和红细胞与血管平滑肌功能障碍有关，而低血红蛋白水平与血管结构异常有关。正常范围内Hct，Hb和RBC的水平升高可能会对脉管系统产生有益影响。