Is the Brain an Early or Late Component of Essential Hypertension?

Nasal turbinate lymphatic obstruction: a proposed new paradigm in the etiology of essential hypertension

Hypertension affects an estimated 1.3 billion people worldwide and is considered the number one contributor to mortality via stroke, heart failure, renal failure, and dementia. Although the physiologic mechanisms leading to the development of essential hypertension are poorly understood, the regulation of cerebral perfusion has been proposed as a primary cause. This article proposes a novel etiology for essential hypertension. Our hypothesis developed from a review of nuclear medicine scans, where the authors observed a significantly abnormal increase in nasal turbinate vasodilation in hypertensive patients using quantitative region of interest analysis. The authors propose that nasal turbinate vasodilation and resultant blood pooling obstruct the flow of cerebrospinal fluid passing through nasal turbinate lymphatics, thereby increasing intracranial pressure. The authors discuss the glymphatic/lymphatic clearance system which is impaired with age, and at which time hypertension also develops. The increased intracranial pressure leads to compensatory hypertension via Cushing's mechanism, i.e., the selfish brain hypothesis. The nasal turbinate vasodilation, due to increased parasympathetic activity, occurs simultaneously along with the well-established increased sympathetic activity of the cardiovascular system. The increased parasympathetic activity is likely due to an autonomic imbalance secondary to the increase in worldwide consumption of processed food. This hypothesis explains the rapid worldwide rise in essential hypertension in the last 50 years and offers a novel mechanism and a new paradigm for the etiology of essential hypertension. This new paradigm offers compelling evidence for the modulation of parasympathetic nervous system activity as a novel treatment strategy, specifically targeting nasal turbinate regulation, to treat diseases such as hypertension, idiopathic intracranial hypertension, and degenerative brain diseases. The proposed mechanism of essential hypertension presented in this paper is a working hypothesis and confirmatory studies will be needed.

Associations of cardiac function and arterial stiffness with cerebrovascular disease

BACKGROUND

White matter hyperintensities (WMHs) represent diffuse small vessel disease implicating the cardiac, systemic, and cerebral vasculatures. As the brain may be the end-organ of cumulative vascular disease, and higher education is protective of both cardiovascular and brain health, we aim to clarify their intertwining relationships.

METHODS

We evaluated participants (mean age = 64) from the UK Biobank with neuroimaging measures of WMHs, left ventricular ejection fraction (LVEF) quantified using cardiovascular MRI, and arterial stiffness index (ASI) quantified using finger photoplethysmography. We used multiple regression to evaluate the basic, independent, and interactive relationships of LVEF status (n = 27,512) and ASI (n = 33,584) with WMHs. Moderated mediation analysis was used to determine whether the relationship between LVEF status and WMH was mediated by ASI and moderated by education.

RESULTS

Abnormal LVEF (β = -0.082, p < 0.001) and higher ASI (β = 0.02, p < 0.001) were associated with greater WMHs separately and independently, but not interactively. Moderated mediation analyses revealed that the relationship between abnormal LVEF and WMH was mediated by ASI, for individuals with lower education (β = -0.004, p < 0.001). Abnormal LVEF was associated with lower cortical thickness in 16 predominantly frontotemporal and select parietal regions (FDR, q < 0.05).

CONCLUSIONS

Cardiovascular dysfunction is associated with regional cerebral atrophy and may precipitate cerebrovascular disease via stiffening of systemic vasculatures, particularly for individuals with lower education. Integrative approaches to study biophysiological vascular systems can elucidate the complex interplay between biological and social determinants of brain and cerebrovascular health.

Cognitive impairment in cerebral small vessel disease induced by hypertension

ABSTRACT

Hypertension is a primary risk factor for the progression of cognitive impairment caused by cerebral small vessel disease, the most common cerebrovascular disease. However, the causal relationship between hypertension and cerebral small vessel disease remains unclear. Hypertension has substantial negative impacts on brain health and is recognized as a risk factor for cerebrovascular disease. Chronic hypertension and lifestyle factors are associated with risks for stroke and dementia, and cerebral small vessel disease can cause dementia and stroke. Hypertension is the main driver of cerebral small vessel disease, which changes the structure and function of cerebral vessels via various mechanisms and leads to lacunar infarction, leukoaraiosis, white matter lesions, and intracerebral hemorrhage, ultimately resulting in cognitive decline and demonstrating that the brain is the target organ of hypertension. This review updates our understanding of the pathogenesis of hypertension-induced cerebral small vessel disease and the resulting changes in brain structure and function and declines in cognitive ability. We also discuss drugs to treat cerebral small vessel disease and cognitive impairment.

Cerebral blood flow regulation and cognitive performance in hypertension

We examined the relation between transcranial Doppler (TCD) markers of cerebral blood flow regulation and cognitive performance in hypertension (HT) patients to evaluate the predictive value of these markers for cognitive decline. We assessed dynamic cerebral autoregulation (dCA), vasoreactivity to carbon dioxide, and neurovascular coupling (NVC) in the middle (MCA) and posterior (PCA) cerebral arteries of 52 patients. Neuropsychological evaluation included the Montreal Cognitive Assessment and tests covering attention, executive function, processing speed, and memory. Notably, reduced rate time in the PCA significantly predicted better processing speed (p = 0.003). Furthermore, reduced overshoot systolic cerebral blood velocity in the PCA and reduced phase in the VLF range in the MCA (p = 0.021 and p = 0.017, respectively) significantly predicted better memory. Intriguingly, enhanced dCA in the MCA predicted poorer memory performance, while reduced NVC in the PCA predicted both superior processing speed and memory performance. These findings suggest that HT-induced changes in cerebral hemodynamics impact cognitive performance. Further research should verify these observations and elucidate whether these changes represent adaptive responses or neurovascular inefficiency. TCD markers might provide insights into HT-related cognitive decline.

Dry eye rate and its relationship with disease stage in patients with primary hypertension: a cross-sectional study in Vietnam

AIM

To determine the dry eye (DE) rate and its relationship with disease stage in patients with primary hypertension.

METHODS

A cross-sectional study included 432 patients with primary hypertension (with an equal number of patients in each group: 144 in stage I, II, and III hypertension) and 144 healthy subjects as a control group. The Ocular Surface Disease Index (OSDI) and Schirmer I test without anesthetics were conducted on all 576 subjects. Subjects with OSDI scores <13 and Schirmer I values equal to or under 10 mm were diagnosed with DE.

RESULTS

The ratio of DE in hypertension patients was higher than in the control group (41.7% versus 18.8%; P<0.001). The proportion of patients with DE increased gradually according to the hypertension stage: 27.1% in stage I, 40.3% in stage II, and 57.6% in stage III, P<0.001. Age, duration of hypertension, plasma urea, creatinine, and high-sensitivity C-reactive protein (CRP-hs) levels in hypertension patients with DE were higher than those without DE, P<0.001. Advanced age, a long duration of hypertension, diabetes mellitus, elevated plasma creatinine, and CRP-hs levels were independent factors associated with DE in primary hypertension patients, P<0.001.

CONCLUSION

DE is a common disorder associated with advanced age, a long duration of hypertension, diabetes mellitus, elevated plasma CRP-hs, and creatinine levels in patients with primary hypertension.

White matter changes underlie hypertension-related cognitive decline in older adults

Hypertension has been well recognized as a risk factor for cognitive impairment and dementia. Although the underlying mechanisms of hypertension-affected cognitive deterioration are not fully understood, white matter changes (WMCs) seem to play an important role. WMCs include low microstructural integrity and subsequent white matter macrostructural lesions, which are common on brain imaging in hypertensive patients and are critical for multiple cognitive domains. This article provides an overview of the impact of hypertension on white matter microstructural and macrostructural changes and its link to cognitive dysfunction. Hypertension may induce microstructural changes in white matter, especially for the long-range fibers such as anterior thalamic radiation (ATR) and inferior fronto-occipital fasciculus (IFOF), and then macrostructural abnormalities affecting different lobes, especially the periventricular area. Different regions' WMCs would further exert different effects to specific cognitive domains and accelerate brain aging. As a modifiable risk factor, hypertension might provide a new perspective for alleviating and delaying cognitive impairment.