The circadian rhythm of arterial blood pressure in Alzheimer disease (AD) patients without hypertension

Obstructive sleep apnea and non-dipper: epiphenomena or risks of Alzheimer's disease?: a review from the HOPE Asia Network

Obstructive sleep apnea (OSA) and associated nocturnal blood pressure (BP) surges is associated with non-dipper. On the other hand, the relationship between neurodegenerative diseases and non-dipper hypertension has been reported. To date, few studies have evaluated the relationships of nocturnal BP dipping patterns and OSA in relation to neurodegenerative diseases, particularly Alzheimer's disease (AD). This review examines the etiology of the association between OSA and the non-dipper pattern of hypertension and how both are involved in the development of AD. To set the stage for this review, we first focus on the pathophysiology of AD, which is interrelated with sleep apnea and non-dipper through dysregulation of central autonomic network.

Association between ambulatory blood pressure monitoring patterns with cognitive function and risk of dementia: a systematic review and meta-analysis

BACKGROUND

The objective of this systematic review and meta-analysis is to investigate whether nocturnal blood pressure fall, expressed by dipping patterns according to 24 h ambulatory blood pressure monitoring (ABPM), is associated with abnormal cognitive function (cognitive impairment or dementia).

METHODS

We systematically searched PubMed, Embase, and Cochrane databases to identify original articles through December 2022. We included any study with at least ten participants reporting on all-cause dementia or cognitive impairment incidence (primary outcome) or validated cognitive tests (secondary outcome) among ABPM patterns. We assessed risk of bias using Newcastle-Ottawa Quality Assessment Scale. We pooled odds ratios (OR) and standardized mean differences (SMD) using random-effect models for primary and secondary outcome, respectively.

RESULTS

In the qualitative synthesis, 28 studies examining 7595 patients were included. The pooled analysis of 18 studies showed that dippers had a 51% [OR 0.49(0.35-0.69)] lower risk of abnormal cognitive function and a 63% [OR 0.37(0.23-0.61)] lower risk of dementia alone, compared to non-dippers. Reverse dippers presented an up to sixfold higher risk [OR 6.06(3.15-11.64)] of abnormal cognitive function compared to dippers and an almost twofold higher risk [OR 1.81(1.26-2.6)] compared to non-dippers. Reverse dippers performed worse in global function neuropsychological tests compared with both dippers [SMD - 0.66(- 0.93 to - 0.39)] and non-dippers [SMD - 0.35(- 0.53 to - 0.16)].

CONCLUSION

Dysregulation of the normal circadian BP rhythm, specifically non-dipping and reverse dipping is associated with abnormal cognitive function. Further studies are required to determine potential underlying mechanisms and possible prognostic or therapeutic implications.

PROTOCOL REGISTRATION

PROSPERO database (ID: CRD42022310384).

Circadian disruption and sleep disorders in neurodegeneration

Disruptions of circadian rhythms and sleep cycles are common among neurodegenerative diseases and can occur at multiple levels. Accumulating evidence reveals a bidirectional relationship between disruptions of circadian rhythms and sleep cycles and neurodegenerative diseases. Circadian disruption and sleep disorders aggravate neurodegeneration and neurodegenerative diseases can in turn disrupt circadian rhythms and sleep. Importantly, circadian disruption and various sleep disorders can increase the risk of neurodegenerative diseases. Thus, harnessing the circadian biology findings from preclinical and translational research in neurodegenerative diseases is of importance for reducing risk of neurodegeneration and improving symptoms and quality of life of individuals with neurodegenerative disorders via approaches that normalize circadian in the context of precision medicine. In this review, we discuss the implications of circadian disruption and sleep disorders in neurodegenerative diseases by summarizing evidence from both human and animal studies, focusing on the bidirectional links of sleep and circadian rhythms with prevalent forms of neurodegeneration. These findings provide valuable insights into the pathogenesis of neurodegenerative diseases and suggest a promising role of circadian-based interventions.

The Association Between 24-Hour Blood Pressure Profiles and Dementia

Midlife hypertension increases risk for dementia. Around one third of adults have diagnosed hypertension; however, many adults are undiagnosed, or remain hypertensive despite diagnosis or treatment. Since blood pressure (BP) follows a circadian rhythm, ambulatory BP monitoring allows for the assessment of BP over a 24-hour period and provides an important tool for improving the diagnosis and management of hypertension. The measurement of 24-hour BP profiles, especially nocturnal BP, demonstrate better predictive ability for cardiovascular disease and mortality than office measurement. However, few studies have examined 24-hour BP profiles with respect to dementia risk. This is an important topic since improvements in BP management could facilitate the primary prevention of vascular cognitive impairment and dementia. Therefore, this review discusses the evidence linking BP to dementia, with a focus on whether the implementation of 24-hour BP measurements can improve risk prediction and prevention strategies. Pathways linking nocturnal BP to dementia are also discussed as are risk reduction strategies. Overall, limited research suggests an association between 24-hour BP elevation and poorer cognition, cerebral small vessel disease, and dementia. However, most studies were cross-sectional. Further evidence is needed to substantiate 24-hour BP profiles, over and above office BP, as predictors of vascular cognitive impairment and incident dementia.

Metabolic determinants of Alzheimer's disease: A focus on thermoregulation

Alzheimer's disease (AD) is a complex age-related neurodegenerative disease, associated with central and peripheral metabolic anomalies, such as impaired glucose utilization and insulin resistance. These observations led to a considerable interest not only in lifestyle-related interventions, but also in repurposing insulin and other anti-diabetic drugs to prevent or treat dementia. Body temperature is the oldest known metabolic readout and mechanisms underlying its maintenance fail in the elderly, when the incidence of AD rises. This raises the possibility that an age-associated thermoregulatory deficit contributes to energy failure underlying AD pathogenesis. Brown adipose tissue (BAT) plays a central role in thermogenesis and maintenance of body temperature. In recent years, the modulation of BAT activity has been increasingly demonstrated to regulate energy expenditure, insulin sensitivity and glucose utilization, which could also provide benefits for AD. Here, we review the evidence linking thermoregulation, BAT and insulin-related metabolic defects with AD, and we propose mechanisms through which correcting thermoregulatory impairments could slow the progression and delay the onset of AD.

Ambulatory Blood Pressure Characteristics of Patients with Alzheimer's Disease: A Multicenter Study from China

BACKGROUND

Previous studies revealed that abnormal blood pressure (BP) plays an important role in the pathogenesis of Alzheimer's disease (AD). However, little is known about the ambulatory BP characteristics of AD in the mild or severe stage.

OBJECTIVE

We explored the ambulatory BP characteristics of AD in the mild or severe stage.

METHODS

In the present study, 106 AD patients (42.5%male, average age 81.6 years) were enrolled from three centers in China. Clinal BP measurements at the supine and standing positions, neurological evaluations, and the 24 h ambulatory BP monitoring were performed.

RESULTS

In the 106 AD patients, 49.2%, 36.8%, and 70%of patients had 24 h, daytime, and nighttime systolic hypertension, respectively, while 19.8%, 29.2%, and 5.7%had 24 h, daytime, and nighttime diastolic hypotension. The prevalence of the reduced and reverse dipping pattern was 34.0%and 48.1%for systolic BP and 32.1%and 45.3%for diastolic BP, respectively. The daytime diastolic BP was significantly correlated with cognitive performance. After adjustment for age, sex, and body mass index, only daytime diastolic BP was associated with remarkable cognitive deterioration (p≤0.008). Further, AD patients in the severe stage had significantly lower levels of the 24 h, daytime, and nighttime diastolic BP, compared with those in the mild stage.

CONCLUSION

In general, AD patients were featured with high nighttime systolic BP, low daytime diastolic BP, and abnormal circadian BP rhythm of reduced and reverse dipping. The diastolic BP, especially daytime diastolic BP, was adversely correlated with the cognitive deterioration in AD.

The connections of Locus Coeruleus with hypothalamus: potential involvement in Alzheimer's disease

The hypothalamus and Locus Coeruleus (LC) share a variety of functions, as both of them take part in the regulation of the sleep/wake cycle and in the modulation of autonomic and homeostatic activities. Such a functional interplay takes place due to the dense and complex anatomical connections linking the two brain structures. In Alzheimer's disease (AD), the occurrence of endocrine, autonomic and sleep disturbances have been associated with the disruption of the hypothalamic network; at the same time, in this disease, the occurrence of LC degeneration is receiving growing attention for the potential roles it may have both from a pathophysiological and pathogenetic point of view. In this review, we summarize the current knowledge on the anatomical and functional connections between the LC and hypothalamus, to better understand whether the impairment of the former may be responsible for the pathological involvement of the latter, and whether the disruption of their interplay may concur to the pathophysiology of AD. Although only a few papers specifically explored this topic, intriguingly, some pre-clinical and post-mortem human studies showed that aberrant protein spreading and neuroinflammation may cause hypothalamus degeneration and that these pathological features may be linked to LC impairment. Moreover, experimental studies in rodents showed that LC plays a relevant role in modulating the hypothalamic sleep/wake cycle regulation or neuroendocrine and systemic hormones; in line with this, the degeneration of LC itself may partly explain the occurrence of hypothalamic-related symptoms in AD.

Circadian and Sleep Dysfunctions in Neurodegenerative Disorders-An Update

Disruptions of sleep and circadian rhythms are among the most debilitating symptoms in patients with neurodegenerative diseases. Their underlying pathophysiology is multilayered and multifactorial. Recent evidence suggests that sleep and circadian disturbances may influence the neurodegenerative processes as well as be their consequence. In this perspective, we provide an update of the current understanding of sleep and circadian dysregulation in Alzheimer's, Parkinson's, and Huntington's diseases.

Circadian alterations in patients with neurodegenerative diseases: Neuropathological basis of underlying network mechanisms

Circadian organization of physiology and behavior is an important biological process that allows organisms to anticipate and prepare for daily changes and demands. Disruptions in this system precipitates a wide range of health issues. In patients with neurodegenerative diseases, alterations of circadian rhythms are among the most common and debilitating symptoms. Although a growing awareness of these symptoms has occurred during the last decade, their underlying neuropathophysiological circuitry remains poorly understood and consequently no effective therapeutic strategies are available to alleviate these health issues. Recent studies have examined the neuropathological status of the different neural components of the circuitry governing the generation of circadian rhythms in neurodegenerative diseases. In this review, we will dissect the potential contribution of dysfunctions in the different nodes of this circuitry to circadian alterations in patients with neurodegenerative diseases. A deeper understanding of these mechanisms will provide not only a better understanding of disease neuro-pathophysiology, but also hold the promise for developing effective and mechanisms-based therapies.

Association between abnormal nocturnal blood pressure profile and dementia in Parkinson's disease

BACKGROUND

Circadian blood pressure alterations are frequently observed in Parkinson's disease, but the association between these changes and dementia in the condition remains unclear. Here, we assess the relationship between abnormal nocturnal blood pressure profiles and dementia in Parkinson's disease.

METHODS

We enrolled 137 patients with Parkinson's disease, who underwent 24 h ambulatory blood pressure monitoring, following cognitive and clinical assessment.

RESULTS

Twenty-seven patients (19.7%) were diagnosed with dementia in this cohort. We observed significant associations of dementia with age, male gender, Hoehn-Yahr (H-Y) stage, diabetes mellitus, history of stroke, presence of cerebrovascular lesions on MRI, and orthostatic hypotension. Univariate logistic regression analysis showed that among the patterns of nocturnal blood pressure profiles, the riser pattern was significantly associated with dementia (OR 11.6, 95%CI: 2.14-215.0, P < 0.01), and this trend was observed after adjusting for all confounding factors except orthostatic hypotension (OR 19.2, 95%CI: 1.12-1960.3, P = 0.04). However, coexistence of a riser pattern and orthostatic hypotension was related to a higher prevalence of dementia (45.2%) than was a riser pattern alone (9.5%). Furthermore, coexistence of a riser pattern and orthostatic hypotension was significantly more associated with dementia than was a riser pattern alone, even after adjusting for confounders (OR 1625.1, 95%CI: 21.9-1343909.5, P < 0.01).

CONCLUSIONS

Our results suggest a relationship between a riser pattern coexisting with orthostatic hypotension and dementia in Parkinson's disease. Further prospective studies are warranted to investigate whether abnormal nocturnal blood pressure profiles predict dementia in Parkinson's disease.

Screening for Cognitive Impairment by Model-Assisted Cerebral Blood Flow Estimation

OBJECTIVE

Alzheimer's disease (AD) is a progressive and debilitating neurodegenerative disease; a major health concern in the ageing population with an estimated prevalence of 46 million dementia cases worldwide. Early diagnosis is therefore crucial so mitigating treatments can be initiated at an early stage. Cerebral hypoperfusion has been linked with blood-brain barrier dysfunction in the early stages of AD, and screening for chronic cerebral hypoperfusion in individuals has been proposed for improving the early diagnosis of AD. However, ambulatory measurements of cerebral blood flow are not routinely carried out in the clinical setting. In this study, we combine physiological modeling with Holter blood pressure monitoring and carotid ultrasound imaging to predict 24-h cerebral blood flow (CBF) profiles in individuals. One hundred and three participants [53 with mild cognitive impairment (MCI) and 50 healthy controls] underwent model-assisted prediction of 24-h CBF. Model-predicted CBF and neuropsychological tests were features in lasso regression models for MCI diagnosis.

RESULTS

A CBF-enhanced classifier for diagnosing MCI performed better, area-under-the-curve (AUC) = 0.889 (95%-CI: 0.800 to 0.978), than a classifier based only on the neuropsychological test scores, AUC = 0.818 (95%-CI: 0.643 to 0.992). An additional cohort of 25 participants (11 MCI and 14 healthy) was recruited to perform model validation by arterial spin-labeling magnetic resonance imaging, and to establish a link between measured CBF that predicted by the model.

CONCLUSION

Ultrasound imaging and ambulatory blood pressure measurements enhanced with physiological modeling can improve MCI diagnosis accuracy.

Ambulatory blood pressure monitoring in older people with dementia: a systematic review of tolerability

BACKGROUND

ambulatory blood pressure monitoring (ABPM) may be helpful for the management of hypertension, but little is known about its tolerability in people with dementia.

OBJECTIVE

to review the published evidence to determine the tolerability of ABPM in people with dementia.

METHODS

English language search conducted in MEDLINE and EMBASE, using 'Ambulatory blood pressure' AND 'Dementia' (and associated synonyms) from 1996 to March 2015.

INCLUSION CRITERIA

people diagnosed with dementia AND in whom blood pressure was measured using ABPM. The initial search was undertaken using title and abstract reviews, with selected papers being agreed for inclusion by two reviewers. Potentially eligible papers were assessed, and high-quality papers were retained. Two reviewers agreed the abstracted data for analysis. Meta-analysis was used to combine results across studies.

RESULTS

of the 221 screened abstracts, 13 studies (6%) met inclusion criteria, 5 had sufficient data and were of sufficient quality, involving 461 participants, most of whom had mild-moderate dementia. 77.7% (95% CI 62.2-93.2%) were able to tolerate ABPM; agreement with office BP was moderate to weak (two studies only-coefficients 0.3-0.38 for systolic blood pressure and 0.11-0.32 for diastolic blood pressure). One study compared home BP monitoring by a relative or ambulatory BP monitoring with office BP measures and found high agreement (κ 0.81). The little available evidence suggested increased levels of dementia being associated with reduced tolerability.

CONCLUSIONS

ABPM is well tolerated in people with mild-moderate dementia and provides some additional information over and above office BP alone. However, few studies have addressed ABPM in people with more severe dementia.

Association between high nocturnal blood pressure and white matter change and its interaction by obstructive sleep apnoea among normotensive adults

OBJECTIVES

A reverse dipping pattern, characterized by higher night-time blood pressure (BP) than daytime BP, is associated with the increased risk for cerebrovascular disease, cardiovascular events and all-cause mortality. However, little has known about the association between white matter change (WMC) and reverse dipping pattern, particularly in normotensive adults. We aimed to examine whether WMC is associated with BP dipping patterns as measured with a 24-h ambulatory BP monitoring and whether obstructive sleep apnoea (OSA) is involved in this relationship

METHODS

: A total of 703 normotensive adults were from an ongoing longitudinal study in a general population. WMC was measured with brain MRI. BP dipping patterns were defined as the ratio of the change in night-time and daytime SBP. OSA was categorized with the apnoea-hypopnea index, as measured with polysomnography. To avoid the influence of hypertensive medications, we only included normotensive adults for the final analysis. To examine the associations between WMC and dipping patterns, we built logistic models. To elucidate the role of OSA, we also conducted both modification and mediation tests.

RESULTS

Reverse dipping pattern was significantly associated with WMC (odds ratio 1.49, 95% confidence interval 1.02-2.18). Further, OSA modified the association between dipping patterns and WMC (P = 0.0118). No mediation effect of OSA was assessed.

CONCLUSION

In 703 normotensive adults, the reverse dipping pattern showed a significant association with WMC, after adjusting for covariates. Further, according to the presence of OSA, the association between reverse dipping and WMC was varied.

High daytime and nighttime ambulatory pulse pressure predict poor cognitive function and mild cognitive impairment in hypertensive individuals

High blood pressure accelerates normal aging stiffness process. Arterial stiffness (AS) has been previously associated with impaired cognitive function and dementia. Our aims are to study how cognitive function and status (mild cognitive impairment, MCI and normal cognitive aging, NCA) relate to AS in a community-based population of hypertensive participants assessed with office and 24-hour ambulatory blood pressure measurements. Six hundred ninety-nine participants were studied, 71 had MCI and the rest had NCA. Office pulse pressure (PP), carotid-femoral pulse wave velocity, and 24-hour ambulatory PP monitoring were collected. Also, participants underwent a brain magnetic resonance to study cerebral small-vessel disease (cSVD) lesions. Multivariate analysis-related cognitive function and cognitive status to AS measurements after adjusting for demographic, vascular risk factors, and cSVD. Carotid-femoral pulse wave velocity and PP at different periods were inversely correlated with several cognitive domains, but only awake PP measurements were associated with attention after correcting for confounders (beta = -0.22, 95% confidence interval (CI) -0.41, -0.03). All ambulatory PP measurements were related to MCI, which was independently associated with nocturnal PP (odds ratio (OR) = 2.552, 95% CI 1.137, 5.728) and also related to the presence of deep white matter hyperintensities (OR = 1.903, 1.096, 3.306). Therefore, higher day and night ambulatory PP measurements are associated with poor cognitive outcomes.

The hypothalamus in Alzheimer's disease: a Golgi and electron microscope study

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, characterized by irreversible decline of mental faculties, emotional and behavioral changes, loss of motor skills, and dysfunction of autonomic nervous system and disruption of circadian rhythms (CRs). We attempted to describe the morphological findings of the hypothalamus in early cases of AD, focusing our study mostly on the suprachiasmatic nucleus (SCN), the supraoptic nucleus (SON), and the paraventricular nucleus (PVN). Samples were processed for electron microscopy and silver impregnation techniques. The hypothalamic nuclei demonstrated a substantial decrease in the neuronal population, which was particularly prominent in the SCN. Marked abbreviation of dendritic arborization, in association with spinal pathology, was also seen. The SON and PVN demonstrated a substantial number of dystrophic axons and abnormal spines. Alzheimer's pathology, such as deposits of amyloid-β peptide and neurofibrillary degeneration, was minimal. Electron microscopy revealed mitochondrial alterations in the cell body and the dendritic branches. The morphological alterations of the hypothalamic nuclei in early cases of AD may be related to the gradual alteration of CRs and the instability of autonomic regulation.

The polymorphism of ARNTL2 (BMAL2) gene rs2306074 C>T is associated with susceptibility of Alzheimer disease in Chinese population

In the present study, we investigated whether polymorphism of ARNTL2 (BMAL2) gene rs2306074 T/C was associated with susceptibility of Alzheimer disease (AD) in Chinese population. A case-control method was employed in this study. 296 unrelated AD patients and 423 control subjects were recruited in current study. The prevalence of C carriers in BMAL2 gene rs2306074 T/C in AD patients was significantly higher than that of control subjects in both the whole sample and APOE ε 4 non-carriers (in the whole sample: χ (2) = 5.938, P = 0.012; in APOE ε 4 non-carriers: χ (2) = 9.048, P < 0.0001). In addition, both in the whole sample and APOE ε 4 non-carriers, prevalence of CC genotypes in BMAL2 gene rs2306074 of AD patients was also significantly higher than that in controls (in the whole sample: χ (2) = 5.126, P = 0.018; in APOE ε 4 non-carriers: χ (2) = 7.389, P = 0.023). However, there was no significant difference of prevalence of C carriers and CC genotypes in BMAL2 gene rs2306074 T/C between AD patients and control subjects among APOE ε 4 carriers (C carriers: χ (2) = 0.020, P = 0.900; CC genotypes: χ (2) = 0.017, P = 0.946). C carriers in BMAL2 gene rs2306074 T/C are associated with a high susceptibility of AD among APOE ε 4 non-carriers but not among APOE ε 4 carriers in Chinese population.