Hypertension has been associated with cognitive impairment and motor function abnormalities possibly linked to alterations in microstructural brain tissue. Near-infrared spectroscopy (NIRS) is a technique that allows the assessment of functional activation of cerebral cortex during a motor task, by measuring the relative changes in oxygenated haemoglobin concentration [O2Hb]. Therefore, we used NIRS technology to examine (i) whether functional activation of human cerebral cortex during handgrip exercise is altered in patients with hypertension and (ii) whether the cerebral [O2Hb] response during exercise is linked to exaggerated systemic blood pressure (BP) responses in hypertensive patients.Design and method:
Twenty-five new-diagnosed hypertensives and 25 normotensives underwent physical examination and ambulatory BP measurement. Following assessment of handgrip maximal voluntary contraction (MVC), each participant performed a testing protocol involving a seated rest (baseline), a 3-min handgrip exercise at 30% MVC, and a 3-min recovery. A continuous-wave functional NIRS was used to monitor changes in cerebral-[O2Hb]. A pair of optodes were placed over the left frontal lobe (4.5 cm inter-optode distance). Beat-by-beat blood pressure (Finapres) was continuously monitored. Intima-media thickness (IMT, ALOCA ultrasound), Augmentation Index (AI) and central pressures (CPs, Sphygmocor) were assessed.Results:
No significant differences in age, BMI, sex, MVC and absolute force maintained during handgrip were detected between groups. Systolic and diastolic BP were higher (p < 0.05) throughout the protocol in hypertensives vs. the vormotensives. During handgrip, cerebral [O2Hb] increased in both groups; however, hypertensive patients exhibited a significantly lower average response in [O2Hb] than normotensives (1.7 ± 1.1 vs. 2.7 ± 2.1, μM respectively; p < 0.05) and a lower [O2Hb] peak response (4.7 ± 2.1 vs. 7.1 ± 4.1 μM; p < 0.01). Significant negative correlations (r = −0.30 to −0.43; p < 0.05) were found between the average response in cerebral-[O2Hb] during handgrip and ambulatory day-diastolic BP, aortic- and peripheral-diastolic BP, AI, as well as with the magnitude of increase in diastolic BP during exercise.Conclusions:
Hypertensive patients exhibited a blunted response in cerebral [O2Hb] during a handgrip exercise stimulus compared with their normotensive counterparts. The blunted increase in cerebral oxygenation during exercise was linked (i) to an exaggerated exercise diastolic BP during handgrip and (ii) to indices of macrovascular stiffening.