Effects of Aerobic Exercise Training on Carotid Arterial Stiffness and Brain Health in Traumatic Brain Injury

Date

2020-05-01T05:00:00.000Z

Authors

Le, Tran B.

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Abstract

BACKGROUND: Vascular dysfunction and hypoperfusion in the brain are common after traumatic brain injury (TBI). The brain is perfused by elastic central arteries that decrease in compliance with age, leading to decreased ability to dampen hemodynamic pulsatility and decreased continuous blood flow in cerebral vasculature. Aerobic exercise improves cardiorespiratory fitness, health status, quality of life, and cognitive function as well as decrease mortality in normal adults. In this regard, physical activity, particularly aerobic exercise training (AET), may have favorable effects on TBI-related vascular and cerebral blood flow (CBF) changes. However, knowledge gaps regarding the effects of chronic TBI on vascular function still exist. Furthermore, little is known about the effect of AET on carotid arterial stiffness and CBF in patients with TBI with pre-existing brain injury. OBJECTIVE: We hypothesized that TBI patients may continue to suffer from vascular impairments at the chronic stage and may benefit from aerobic exercise with improvements in cardiorespiratory fitness, decrease in carotid arterial stiffness, and improved brain health. METHODS: Twenty-three participants with a history of mild to severe TBI and twenty-five age- gender-fitness level-matched participants with no history of TBI were recruited for the normal control group (non-TBI). All participants were 18-65 years old and have a sedentary lifestyle. The groups were divided into young (19-44 years old) and middle-aged (45-63 years old) for further analysis. Carotid arterial compliance was measured using common carotid artery echography and applanation tonometry. Transcranial Doppler was used to measure the cerebral blood flow velocities. Carotid arterial compliance was calculated from the carotid diameters and blood pressures. Seventeen of the TBI survivors (age: 48±13 years, 10 women) with persistent neurological symptoms 6-60 months after initial injury were randomized to 3-month moderate-intensity AET or control stretching program (SAT) and completed the interventions. Among them, 10 sustained mild TBI and 7 had moderate to severe TBI. Cardiorespiratory fitness was assessed by peak oxygen uptake (VO2peak) using a modified Astrand-Saltin treadmill protocol. Carotid arterial compliance was measured as measured. Neuropsychological function was assessed using the NIH Toolbox cognition battery and the PROMIS assessment. RESULTS: In the cross-sectional portion of the study, hemodynamic parameters indicate that the TBI group had higher brachial blood pressure (116.4 ± 10.4 vs. 109.8 ± 9.3 mmHg, p < 0.05). and carotid systolic blood pressure (113.0 ± 11.0 vs. 102.8 ± 10.6 mmHg, p < 0.05) than the non-TBI groups at rest. Arterial compliance was significantly lower in the TBI vs. non-TBI group (0.101 + 0.025 vs. 0.120 + 0.029 mm2/mmHg, p < 0.05). Additionally, cerebrovascular resistance was significantly higher in the TBI vs. non-TBI group (0.168 + 0.0332 vs. 0.145 + 0.0290 mmHg/mL/min, p < 0.05). Ten participants were randomized to AET group and seven to stretching group. No age, gender, or VO2peak differences were noted at baseline between AET and stretching groups. The duration of the intervention was twelve weeks. Although no statistically significant changes were observed following the intervention, different trends were observed. VO2peak increased by 7% in AET yet decreased by 4% in stretching; arterial compliance increased by 12 % in AET and decreased by 2% in stretching; NIH Toolbox fluid composite score, which assessed adaptability to new experience, improved by 15% in AET and 9% in stretching; and the NIH Toolbox total composite score, which involves adaptability to new experiences as well as past knowledge and skills, improved by 7% in AET versus 4% in stretching. CONCLUSION: The results suggest that TBI is associated with increased blood pressure, which is consistent with existing literature. The elevated blood pressure potentially leads is associated with decreased arterial compliance and increased resistance in the cerebral vasculature. Previous literature suggests that decreased cerebral blood flow may be associated with the cognitive impairment in TBI patients. For the longitudinal portion of the study, the physiological measurements (includingVO2peak, arterial compliance, and pulsatility index) and cognitive measurements suggest the potential positive effect of AET on physiological and cognitive improvement in patients with TBI. Physical activity, both SAT and AET, can improve arterial compliance in patients with chronic TBI.

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