Wolfson Centre for Prevention of Stroke and Dementia, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
Eur Stroke J. 2024 Sep;9(3):772-780. doi: 10.1177/23969873241245631. Epub 2024 Apr 18.
Cerebral blood flow (CBF) declines with age and abnormalities in CBF are associated with age-related cerebrovascular disease and neurodegeneration. Women have higher CBF than men, although this sex-difference diminishes to some extent with age in healthy subjects. The physiological drivers of these age/sex differences are uncertain, but might be secondary to age and sex-differences in haemoglobin (Hb) level. Hb levels are inversely correlated with CBF, are lower in women, and decline with age in men, but the interrelations between these factors have not been explored systematically either in healthy subjects or across the full age-range in patients with vascular risk factors. We aimed to determine the age-specific interrelations between sex, Hb, and CBF velocity in a large cohort of patients with cerebrovascular disease.
In patients with a recent transient ischaemic attack or minor stroke (Oxford Vascular Study) and no ipsilateral or contralateral stenosis of the carotid or intracranial arteries, we related peak-systolic velocity (PSV) and other parameters on transcranial Doppler ultrasound (TCD) of the middle cerebral artery to sex, age, Hb and vascular risk factors.
Of 958 eligible subjects (mean age/SD = 68.04/14.26, 53.2% male), younger women (age < 55 years) had higher CBF velocities than men (mean sex difference in PSV at age < 55 years = 16.31 cm/s; < 0.001), but this difference declined with age (interaction < 0.001), such that it was no longer significant at age 75-84 (∆PSV = 3.26 cm/s; = 0.12) and was reversed at age ⩾ 85 (∆PSV = -7.42 cm/s; = 0.05). These changes mirrored trends in levels of Hb, which were higher in men at age < 55 (∆Hb = 1.92 g/dL; < 0.001), but steadily decreased with age in men but not in women (interaction < 0.001), with no residual sex-difference at age ⩾ 85 (∆Hb = 0.12 g/dL; = 0.70). There was an inverse correlation between Hb and PSV in both women and men (both ⩽ 0.01), and the sex-difference in PSV at age < 55 was substantially diminished after adjustment for Hb (∆PSV = 6.92; = 0.036; ∆PSV = 5.92, = 0.13 with further adjustment for end-tidal CO). In contrast, the sex difference in PSV was unaffected by adjustment for systolic and diastolic blood pressure, heart rate, and vascular risk factors (history of hypertension, diabetes, hyperlipidaemia and smoking).
CBF velocity is strongly correlated with Hb level at all ages, and sex-differences in CBF velocity appear to be explained in major part by age-related sex-differences in Hb.
脑血流量（CBF）随年龄增长而下降，CBF 异常与年龄相关的脑血管疾病和神经退行性变有关。女性的 CBF 高于男性，尽管在健康受试者中，这种性别差异随着年龄的增长在某种程度上会减小。这些年龄/性别差异的生理驱动因素尚不确定，但可能与血红蛋白（Hb）水平的年龄和性别差异有关。Hb 水平与 CBF 呈负相关，女性较低，男性随年龄增长而下降，但在健康受试者或血管危险因素患者的整个年龄范围内，这些因素之间的相互关系尚未得到系统研究。我们旨在确定在一大群患有脑血管疾病的患者中，性别、Hb 和大脑中动脉经颅多普勒超声（TCD）中峰值收缩速度（PSV）等参数之间的特定年龄相关性。
在近期短暂性脑缺血发作或小卒中（牛津血管研究）的患者中，且没有同侧或对侧颈动脉或颅内动脉狭窄的患者中，我们将大脑中动脉 TCD 的 PSV 和其他参数与性别、年龄、Hb 和血管危险因素相关联。
在 958 名合格受试者中（平均年龄/标准差=68.04/14.26，53.2%为男性），年轻女性（年龄<55 岁）的 CBF 速度高于男性（年龄<55 岁时 PSV 的平均性别差异为 16.31cm/s；<0.001），但这种差异随着年龄的增长而下降（交互作用<0.001），以至于在 75-84 岁时不再显著（ΔPSV=3.26cm/s；=0.12），在年龄≥85 岁时则相反（ΔPSV=-7.42cm/s；=0.05）。这些变化反映了 Hb 水平的趋势，在年龄<55 岁的男性中，Hb 水平较高（ΔHb=1.92g/dL；<0.001），但随着年龄的增长，男性的 Hb 水平稳步下降，而女性则没有（交互作用<0.001），在年龄≥85 岁时，不再存在性别差异（ΔHb=0.12g/dL；=0.70）。Hb 和 PSV 在女性和男性中均呈负相关（均<0.01），并且在调整 Hb 后，年龄<55 岁时 PSV 的性别差异明显减小（ΔPSV=6.92；=0.036；ΔPSV=5.92，=0.13，进一步调整呼气末 CO）。相比之下，PSV 的性别差异不受调整收缩压和舒张压、心率和血管危险因素（高血压、糖尿病、高脂血症和吸烟史）的影响。
CBF 速度与所有年龄段的 Hb 水平密切相关，CBF 速度的性别差异似乎主要由 Hb 水平的年龄相关性别差异解释。
