Severity of Traumatic Brain Injury in Older Adults and Risk of Ischemic Stroke and Depression

Elevated Risk of Stroke in Young Adults After Traumatic Brain Injury: A Nationwide Study of 1 Million Individuals

BACKGROUND

Although stroke is commonly perceived as occurring in older adults, traumatic brain injury, one of the risk factors for stroke, is a leading cause of death in the younger adults. This study evaluated stroke risk in young-to-middle-aged adults based on traumatic brain injury severity and stroke subtypes.

METHODS AND RESULTS

For this retrospective, population-based, cohort study, data of adults aged 18 to 49 years who were diagnosed with traumatic brain injury were obtained from the Korean National Health Insurance Service between 2010 and 2017. Traumatic brain injury history was measured based on the International Classification of Diseases, Tenth Revision (ICD-10), codes. Posttraumatic brain injury stroke risk was analyzed using a time-dependent Cox regression model. At baseline, 518423 patients with traumatic brain injury and 518 423 age- and sex-matched controls were included. The stroke incidence rate per 1000 person-years was 3.82 in patients with traumatic brain injury and 1.61 in controls. Stroke risk was approximately 1.89 times as high in patients with traumatic brain injury (hazard ratio, 1.89 [95% CI, 1.84-1.95]). After excluding stroke cases that occurred within 12 months following traumatic brain injury, these significant associations remained. In the subgroup analysis, patients with brain injury other than concussion had an approximately 9.34-fold risk of intracerebral hemorrhage than did the controls.

CONCLUSIONS

Stroke prevention should be a priority even in young-to-middle-aged adult patients with traumatic brain injury. Managing stroke risk factors through regular health checkups and modifying health-related behaviors is necessary to prevent stroke.

Dysregulation of the dopaminergic system secondary to traumatic brain injury: implications for mood and anxiety disorders

Traumatic brain injury (TBI) represents a public health issue with a high mortality rate and severe neurological and psychiatric consequences. Mood and anxiety disorders are some of the most frequently reported. Primary and secondary damage can cause a loss of neurons and glial cells, leading to dysfunction of neuronal circuits, which can induce imbalances in many neurotransmitter systems. Monoaminergic systems, especially the dopaminergic system, are some of the most involved in the pathogenesis of neuropsychiatric and cognitive symptoms after TBI. In this work, we summarize the studies carried out in patients who have suffered TBI and describe alterations in the dopaminergic system, highlighting (1) dysfunction of the dopaminergic neuronal circuits caused by TBI, where modifications are shown in the dopamine transporter (DAT) and alterations in the expression of dopamine receptor 2 (D2R) in brain areas with dopaminergic innervation, thus establishing a hypodopaminergic state and (2) variations in the concentration of dopamine and its metabolites in biological fluids of post-TBI patients, such as elevated dopamine (DA) and alterations in homovanillic acid (HVA). On the other hand, we show a large number of reports of alterations in the dopaminergic system after a TBI in animal models, in which modifications in the levels of DA, DAT, and HVA have been reported, as well as alterations in the expression of tyrosine hydroxylase (TH). We also describe the biological pathways, neuronal circuits, and molecular mechanisms potentially involved in mood and anxiety disorders that occur after TBI and are associated with alterations of the dopaminergic system in clinical studies and animal models. We describe the changes that occur in the clinical picture of post-TBI patients, such as alterations in mood and anxiety associated with DAT activity in the striatum, the relationship between post-TBI major depressive disorders (MDD) with lower availability of the DA receptors D2R and D3R in the caudate and thalamus, as well as a decrease in the volume of the substantia nigra (SN) associated with anxiety symptoms. With these findings, we discuss the possible relationship between the disorders caused by alterations in the dopaminergic system in patients with TBI.

Adolescent traumatic brain injury leads to incremental neural impairment in middle-aged mice: role of persistent oxidative stress and neuroinflammation

Background

Traumatic brain injury (TBI) increases the risk of mental disorders and neurodegenerative diseases in the chronic phase. However, there is limited neuropathological or molecular data on the long-term neural dysfunction and its potential mechanism following adolescent TBI.

Methods

A total of 160 male mice aged 8 weeks were used to mimic moderate TBI by controlled cortical impact. At 1, 3, 6 and 12 months post-injury (mpi), different neurological functions were evaluated by elevated plus maze, forced swimming test, sucrose preference test and Morris water maze. The levels of oxidative stress, antioxidant response, reactive astrocytes and microglia, and expression of inflammatory cytokines were subsequently assessed in the ipsilateral hippocampus, followed by neuronal apoptosis detection. Additionally, the morphological complexity of hippocampal astrocytes was evaluated by Sholl analysis.

Results

The adolescent mice exhibited persistent and incremental deficits in memory and anxiety-like behavior after TBI, which were sharply exacerbated at 12 mpi. Depression-like behaviors were observed in TBI mice at 6 mpi and 12 mpi. Compared with the age-matched control mice, apoptotic neurons were observed in the ipsilateral hippocampus during the chronic phase of TBI, which were accompanied by enhanced oxidative stress, and expression of inflammatory cytokines (IL-1β and TNF-α). Moreover, the reactive astrogliosis and microgliosis in the ipsilateral hippocampus were observed in the late phase of TBI, especially at 12 mpi.

Conclusion

Adolescent TBI leads to incremental cognitive dysfunction, and depression- and anxiety-like behaviors in middle-aged mice. The chronic persistent neuroinflammation and oxidative stress account for the neuronal loss and neural dysfunction in the ipsilateral hippocampus. Our results provide evidence for the pathogenesis of chronic neural damage following TBI and shed new light on the treatment of TBI-induced late-phase neurological dysfunction.

Prevalence and characteristics of comorbid stroke and traumatic brain injury in a real-world population: findings from a nationally representative cross-sectional survey in China

BACKGROUND

In China, data on the prevalence and characteristics of comorbid stroke and traumatic brain injury (TBI) in real-world populations are still lacking but of paramount importance for the evidence-based prevention and control of the comorbidity of the two diseases. This study aimed to investigate the prevalence and characteristics of comorbid stroke and TBI in a real-world population.

METHODS

In 2013, a nationally representative, door-to-door survey on stroke and TBI using a complex, multistage, probability sampling design was conducted among approximately 600,000 participants from 155 urban and rural areas in China (Ethic ID: KY2013-006-01). The weighted prevalence of comorbid stroke and TBI was estimated using individuals' final weight. A Poisson regression analysis was used to compare the rate ratio of the comorbidity prevalence among different subgroups of the population, including age, sex, place of residence, and geographic location subgroups. For analyses of associations between the comorbidities and predictors of interest, all other variables were adjusted for in a multinomial logistic regression model.

RESULTS

Among the 596,536 people, 219 patients with comorbid stroke and TBI were identified. The point prevalence of comorbid stroke and TBI weighted to the China 2010 census population was 29.30 (95% CI: 22.69-37.84) per 100,000 population in China. The adjusted prevalence of post-TBI stroke in patients with previous TBI was significantly higher than that of post-stroke TBI in patients with previous stroke (6021.3 vs. 811.1 per 100,000 people; rate ratio: 11.001; 95% CI: 8.069-14.998). Patients with nonconcussion had significantly higher rates of both pre-stroke TBI (odds ratio: 4.694; 95% CI: 3.296-6.687) and post-stroke TBI (odds ratio: 6.735; 95% CI: 3.719-12.194) than patients with concussion. Compared to patients with ischaemic stroke, patients with subarachnoid haemorrhage (odds ratio: 2.044; 95% CI: 1.097-3.809) and intracerebral haemorrhage (odds ratio: 1.903; 95% CI: 1.296-2.795) had significantly higher rates of post-TBI stroke.

CONCLUSIONS

The high prevalence of stroke among TBI patients is becoming a new public health issue. TBI patients, especially those with nonconcussion TBI, are more likely to develop comorbid stroke and TBI than stroke patients, especially ischaemic stroke patients.

Long-term risk of cardiovascular disease after traumatic brain injury: screening and prevention

Traumatic brain injury (TBI) is highly prevalent among individuals participating in contact sports, military personnel, and in the general population. Although it is well known that brain injury can cause neurological and psychiatric complications, evidence from studies on individuals exposed to a single or repetitive brain injuries suggests an understudied association between TBI and the risk of developing chronic cardiovascular diseases and risk factors for cardiovascular disease. Several studies have shown that people without pre-existing comorbidities who sustain a TBI have a significantly higher risk of developing chronic cardiovascular disease, than people without TBI. Similar observations made in military and professional American-style football cohorts suggest causal pathways through which modifiable cardiovascular risk factors might mediate the relationship between brain injury and chronic neurological diseases. A better understanding of cardiovascular disease risk after TBI combined with a proactive, targeted screening programme might mitigate long-term morbidity and mortality in individuals with TBI, and improve their quality of life.

Association Between Traumatic Brain Injury and Increased Risk of Stroke: A Systematic Review and Meta-analysis

OBJECTIVE

To determine whether exposure to traumatic brain injury (TBI) is associated with increased risk of stroke in adults compared with referents not exposed to TBI, and to understand whether an association exists throughout the spectrum of injury severity, whether it differs between the acute and chronic phases after TBI, and whether the association is greater with hemorrhagic compared with ischemic stroke after TBI.

SETTING

A database search was conducted on January 22, 2021. Searches were run in MEDLINE (1946 to present), Embase (1988 to present), Evidence-Based Medicine Reviews (various dates), Scopus (1970 to present), and Web of Science (1975 to present).

DESIGN

Observational studies that quantified the association of stroke after TBI compared with referents without TBI were included. Three coauthors independently reviewed titles and abstracts to determine study eligibility. Study characteristics were extracted independently by 2 coauthors who followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, and study quality was assessed independently by 2 coauthors who used the Newcastle-Ottawa Scale. Random-effects meta-analyses were performed.

MAIN MEASURES

The primary exposure was TBI of any severity, and the primary outcome was stroke of any kind. Subgroup analysis was performed to assess heterogeneity associated with severity of TBI, type of stroke, and time from TBI to stroke.

RESULTS

A total of 64 full-text articles were reviewed, and data were extracted from 8 cohort studies (N = 619 992 individuals exposed to TBI along with nonexposed referents). A significant overall association was found with TBI and stroke (hazard ratio, 2.06; 95% CI, 1.28-3.32). Significant subgroup differences were found with a smaller risk of ischemic stroke compared with stroke of all types (P < .001, I² = 93.9%).

CONCLUSIONS

TBI, regardless of injury severity, was associated with a higher risk of stroke. To improve secondary stroke prevention strategies, future studies should classify TBI severity and type of stroke more precisely and determine long-term risk.

Dihydromyricetin Attenuates Cerebral Ischemia Reperfusion Injury by Inhibiting SPHK1/mTOR Signaling and Targeting Ferroptosis

Background

Dihydromyricetin (DHM) exerts protective effects in various brain diseases. The aim of this research was to investigate the biological role of DHM in cerebral ischemia reperfusion (I/R) injury.

Methods

We generated a rat model of cerebral I/R injury by performing middle cerebral artery occlusion/reperfusion (MCAO/R). The neurological score and brain water content of the experimental rats was then evaluated. The infarct volume and extent of apoptosis in brain tissues was then assessed by 2,3,5-triphenyltetrazolium (TTC) and TdT-mediated dUTP nick end labeling (TUNEL) staining. Hippocampal neuronal cells (HT22) were subjected to oxygen-glucose deprivation/reperfusion (OGD/R) and cell counting kit-8 (CCK-8) assays and flow cytometry were performed to detect cell viability and apoptosis. The levels of lipid reactive oxygen species (ROS) and iron were detected and the expression levels of key proteins were assessed by Western blotting.

Results

DHM obviously reduced neurological deficits, brain water content, infarct volume and cell apoptosis in the brain tissues of MCAO/R rats. DHM repressed ferroptosis and inhibited the sphingosine kinase 1 (SPHK1)/mammalian target of rapamycin (mTOR) pathway in MCAO/R rats. In addition, DHM promoted cell viability and repressed apoptosis in OGD/R-treated HT22 cells. DHM also suppressed the levels of lipid ROS and intracellular iron in OGD/R-treated HT22 cells. The expression levels of glutathione peroxidase 4 (GPX4) was enhanced while the levels of acyl-CoA synthetase long-chain family member 4 (ACSL4) and phosphatidylethanolamine binding protein 1 (PEBP1) were reduced in OGD/R-treated HT22 cells in the presence of DHM. Moreover, the influence conferred by DHM was abrogated by the overexpression of SPHK1 or treatment with MHY1485 (an activator of mTOR).

Conclusion

This research demonstrated that DHM repressed ferroptosis by inhibiting the SPHK1/mTOR signaling pathway, thereby alleviating cerebral I/R injury. Our findings suggest that DHM may be a candidate drug for cerebral I/R injury treatment.

Long-Term Risk of Stroke after Traumatic Brain Injury: A Population-Based Medical Record Review Study

OBJECTIVE

To reliably inform secondary prevention strategies and reduce morbidity and mortality after traumatic brain injury (TBI), we sought to understand the long-term risk of stroke after TBI in patients aged 40 years and older in comparison to age- and sex-matched referents from a population-based cohort.

MATERIALS AND METHODS

TBI cases in Olmsted County, Minnesota from January 1, 1985, to December 31, 1999, were confirmed by manual review, classified by injury severity and mechanism, and nonhead trauma was quantified. Each TBI case was matched to 2 sex- and age-matched population-based referents without TBI and with similar severity nonhead trauma. Records of cases and referents were manually abstracted to confirm stroke diagnosis. Stroke events during initial hospitalization for TBI were excluded.

RESULTS

In total, 1,410 TBI cases were confirmed, 61% classified as possible TBI (least severe, consistent with concussive), with the most common mechanism being falls. There were 162 stroke events among those with TBI (11.5%) and 269 among referents (9.5%). Median time to stroke from the index date for those with TBI was 10.2 years (Q1-Q3 5.2-17.8), and for referents 12.1 years (Q1-Q3 6.2-17.3), p = 0.215. All-severity TBI was associated with increased risk of stroke (HR: 1.32, 95% CI: 1.06-1.63, p = 0.011), but only definite TBI (consistent with moderate-severe) was associated with significant risk (HR: 2.20, 95% CI: 1.04-4.64, p = 0.038) when stratified by severity.

DISCUSSION/CONCLUSION

By confirming TBI cases, stroke diagnoses, and injury severity classification using manual review with levels of accuracy not previously reported, these results indicate moderate-severe TBI increases long-term risk for stroke. These findings confirm the need to regularly assess long-term vascular risk after TBI to implement disease prevention strategies.

miR-129-5p targets FEZ1/SCOC/ULK1/NBR1 complex to restore neuronal function in mice with post-stroke depression

Post-stroke depression (PSD) seriously affects the normal life of patients. Based on the previous sequencing results, this study selected miR-129-5p as the research object, which was significantly reduced in the PSD model by screening. To clarify the regulatory role of miR-129-5p, this study overexpressed and interfered with miR-129-5p in neuronal cells cultured in vitro, tested its effect on neuronal cell autophagy, and determined expressions of fasciculation and elongation protein zeta-1 (FEZ1), short coiled-coil protein (SCOC), unc-51 like autophagy activating kinase 1 (ULK1) and autophagy cargo receptor (NBR1) autophagy-related proteins. The dual-luciferase reporter system and immunoprecipitation were applied to detect the molecular regulatory mechanism of miR-129-5 and FEZ1, SCOC, ULK1 and NBR1. Findings of the present study revealed that the autophagy of neuronal cells was markedly decreased by overexpressing miR-129-5p (p < 0.05), and expressions of FEZ1, SCOC, ULK1 and NBR1 were substantially reduced (p < 0.05). The dual-luciferase reporter system results indicated that FEZ1, SCOC, ULK1 and NBR1 were all miR-129-5p target genes. Furthermore, immunoprecipitation assay revealed that SCOC, ULK1 and NBR1 could directly bind to the FEZ1 protein. The experiments at an animal level demonstrated that miR-129-5p could effectively alleviate the behavioral indicators of PSD model mice. Taken together, this study testified that SCOC/ULK1/NBR1 proteins could directly bind to FEZ1 to form protein complex, and all of the four proteins FEZ1/SCOC/ULK1/NBR1 were miR-129-5p target genes. miR-129-5p overexpression could effectively restore the behavioral characteristics of model mice, and reduce the autophagy-related proteins FEZ1/SCOC/ULK1/NBR1.

Impaired capillary-to-arteriolar electrical signaling after traumatic brain injury

Traumatic brain injury (TBI) acutely impairs dynamic regulation of local cerebral blood flow, but long-term (>72 h) effects on functional hyperemia are unknown. Functional hyperemia depends on capillary endothelial cell inward rectifier potassium channels (Kir2.1) responding to potassium (K+) released during neuronal activity to produce a regenerative, hyperpolarizing electrical signal that propagates from capillaries to dilate upstream penetrating arterioles. We hypothesized that TBI causes widespread disruption of electrical signaling from capillaries-to-arterioles through impairment of Kir2.1 channel function. We randomized mice to TBI or control groups and allowed them to recover for 4 to 7 days post-injury. We measured in vivo cerebral hemodynamics and arteriolar responses to local stimulation of capillaries with 10 mM K+ using multiphoton laser scanning microscopy through a cranial window under urethane and α-chloralose anesthesia. Capillary angio-architecture was not significantly affected following injury. However, K+-induced hyperemia was significantly impaired. Electrophysiology recordings in freshly isolated capillary endothelial cells revealed diminished Ba2+-sensitive Kir2.1 currents, consistent with a reduction in channel function. In pressurized cerebral arteries isolated from TBI mice, K+ failed to elicit the vasodilation seen in controls. We conclude that disruption of endothelial Kir2.1 channel function impairs capillary-to-arteriole electrical signaling, contributing to altered cerebral hemodynamics after TBI.