Baroreflex sensitivity, vascular risk factors, and cognitive function in a healthy elderly population: the PROOF cohort

Influence of a 2-week transcutaneous auricular vagus nerve stimulation on memory: findings from a randomized placebo controlled trial in non-clinical adults

PURPOSE

Memory plays an essential role in daily life and is one of the first functions to deteriorate in cognitive impairment and dementia. Transcutaneous vagus nerve stimulation (tVNS) is a promising therapeutic method; however, its ability to enhance memory is underexplored, especially considering long-term stimulation. We aimed to investigate the effect of a 2-week course of auricular tVNS (taVNS) on memory in a non-clinical population.

METHODS

This single-blind randomized placebo-wait-list controlled trial recruited 76 participants (30 men; mean age 48.32 years) and randomized them into four groups: early active/sham taVNS and late active/sham taVNS. Participation in the study lasted 4 weeks; early groups underwent 2 weeks intervention immediately following the first study site visit (days 0-13) and late groups 2 weeks after the first study site visit (days 14-27). Active and sham taVNS included 2 weeks of daily 4-h neurostimulation at the tragus or earlobe, respectively. To assess memory, we used the Rey Auditory Verbal Learning Test.

RESULTS

Two weeks of active taVNS, but not sham taVNS, improved immediate recall and short-term memory score both in early and late groups. Furthermore, the improvements persisted over subsequent follow-up in early active taVNS. Importantly, the effect of active taVNS was superior to sham for immediate recall in both early and late groups. There were no statistical differences in delayed recall.

CONCLUSION

Our findings suggest that taVNS has potential to improve memory, particularly immediate recall, and may be an effective method in preventing memory loss and mitigating cognitive aging.

Prefrontal activity and heart rate variability during cognitive tasks may show different changes in young and older adults with and without mild cognitive impairment

Background

Age-related decline in cognitive function is often linked to changed prefrontal cortex (PFC) activity and heart rate variability (HRV). Mild cognitive impairment (MCI), a transitional stage between normal aging and dementia, might have further degeneration beyond aging. This study aimed to investigate the differences between young and older adults with or without MCI in cognitive functions, task-induced PFC activation and HRV changes.

Methods

Thirty-one healthy young adults (YA), 44 older adults (OA), and 28 older adults with MCI (OA-MCI) were enrolled and compared in this cross-sectional study. Each participant received a one-time assessment including cognitive and executive functions, as well as the simultaneous recording of PFC activity and HRV during a cognitive task paradigm.

Results

We observed age-related decrease in global cognitive functions, executive functions, HRV, and increase in PFC activity. The MCI further deteriorated the global cognitive and executive performances, but not the HRV or the prefrontal activation.

Conclusion

Older people showed lower performances in general cognitive function and executive function, compensatory increase of PFC activity, and reduced HRV. Older people with MCI had further deterioration in cognitive performance, but not in PFC activation and HRV.

Associations of baseline obstructive sleep apnea and sleep macroarchitecture with cognitive function after 8 years in middle-aged and older men from a community-based cohort study

Previous prospective studies examining associations of obstructive sleep apnea and sleep macroarchitecture with future cognitive function recruited older participants, many demonstrating baseline cognitive impairment. This study examined obstructive sleep apnea and sleep macroarchitecture predictors of visual attention, processing speed, and executive function after 8 years among younger community-dwelling men. Florey Adelaide Male Ageing Study participants (n = 477) underwent home-based polysomnography, with 157 completing Trail-Making Tests A and B and the Mini-Mental State Examination. Associations of obstructive sleep apnea (apnea-hypopnea index, oxygen desaturation index, and hypoxic burden index) and sleep macroarchitecture (sleep stage percentages and total sleep time) parameters with future cognitive function were examined using regression models adjusted for baseline demographic, biomedical, and behavioural factors, and cognitive task performance. The mean (standard deviation) age of the men at baseline was 58.9 (8.9) years, with severe obstructive sleep apnea (apnea-hypopnea index ≥30 events/h) in 9.6%. The median (interquartile range) follow-up was 8.3 (7.9-8.6) years. A minority of men (14.6%) were cognitively impaired at baseline (Mini-Mental State Examination score <28/30). A higher percentage of light sleep was associated with better Trail-Making Test A performance (B = -0.04, 95% confidence interval [CI] -0.06, -0.01; p = 0.003), whereas higher mean oxygen saturation was associated with worse performance (B = 0.11, 95% CI 0.02, 0.19; p = 0.012). While obstructive sleep apnea and sleep macroarchitecture might predict cognitive decline, future studies should consider arousal events and non-routine hypoxaemia measures, which may show associations with cognitive decline.

Cardiovascular autonomic regulation correlates with cognitive performance in patients with a history of traumatic brain injury

BACKGROUND AND OBJECTIVE

Traumatic brain injury (TBI) may afflict brain areas contributing to both cardiovascular autonomic regulation and cognitive performance. To evaluate possible associations between both functions in patients with a history of TBI (post-TBI-patients), we determined correlations between cardiovascular autonomic regulation and cognitive function in post-TBI-patients.

METHODS

In 86 post-TBI-patients (33.1 ± 10.8 years old, 22 women, 36.8 ± 28.9 months after injury), we monitored RR intervals (RRI), systolic and diastolic blood pressures (BPsys, BPdia), and respiration (RESP) at rest. We calculated parameters of total cardiovascular autonomic modulation (RRI-standard-deviation (RRI-SD), RRI-coefficient-of-variation (RRI-CV), RRI-total-powers), sympathetic (RRI-low-frequency-powers (RRI-LF), normalized (nu) RRI-LF-powers, BPsys-LF-powers) and parasympathetic modulation (root-mean-square-of-successive-RRI-differences (RMSSD), RRI-high-frequency-powers (RRI-HF), RRI-HFnu-powers), sympathetic-parasympathetic balance (RRI-LF/HF-ratios), and baroreflex sensitivity (BRS). We used the Mini-Mental State Examination and Clock Drawing Test (CDT) to screen the general global and visuospatial cognitive function, and applied the standardized Trail Making Test (TMT)-A assessing visuospatial abilities and TMT-B assessing executive function. We calculated correlations between autonomic and cognitive parameters (Spearman's rank correlation test; significance: P < 0.05).

RESULTS

CDT values positively correlated with age (P = 0.013). TMT-A values inversely correlated with RRI-HF-powers (P = 0.033) and BRS (P = 0.043), TMT-B values positively correlated with RRI-LFnu-powers (P = 0.015), RRI-LF/HF-ratios (P = 0.036), and BPsys-LF-powers (P = 0.030), but negatively with RRI-HFnu-powers (P = 0.015).

CONCLUSIONS

In patients with a history of TBI, there is an association between decreased visuospatial and executive cognitive performance and reduced parasympathetic cardiac modulation and baroreflex sensitivity with relatively increased sympathetic activity. Altered autonomic control bears an increased cardiovascular risk; cognitive impairment compromises quality of life and living conditions. Thus, both functions should be monitored in post-TBI-patients.

Associations of Baseline Sleep Microarchitecture with Cognitive Function After 8 Years in Middle-Aged and Older Men from a Community-Based Cohort Study

Purpose

Prospective studies examining associations between baseline sleep microarchitecture and future cognitive function recruited from small samples with predominantly short follow-up. This study examined sleep microarchitecture predictors of cognitive function (visual attention, processing speed, and executive function) after 8 years in community-dwelling men.

Patients and Methods

Florey Adelaide Male Ageing Study participants (n=477) underwent home-based polysomnography (2010-2011), with 157 completing baseline (2007-2010) and follow-up (2018-2019) cognitive assessments (trail-making tests A [TMT-A] and B [TMT-B] and the standardized mini-mental state examination [SMMSE]). Whole-night F4-M1 sleep EEG recordings were processed following artifact exclusion, and quantitative EEG characteristics were obtained using validated algorithms. Associations between baseline sleep microarchitecture and future cognitive function (visual attention, processing speed, and executive function) were examined using linear regression models adjusted for baseline obstructive sleep apnoea, other risk factors, and cognition.

Results

The final sample included men aged (mean [SD]) 58.9 (8.9) years at baseline, overweight (BMI 28.5 [4.2] kg/m²), and well educated (75.2% ≥Bachelor, Certificate, or Trade), with majorly normal baseline cognition. Median (IQR) follow-up was 8.3 (7.9, 8.6) years. In adjusted analyses, NREM and REM sleep EEG spectral power was not associated with TMT-A, TMT-B, or SMMSE performance (all p>0.05). A significant association of higher N3 sleep fast spindle density with worse TMT-B performance (B=1.06, 95% CI [0.13, 2.00], p=0.026) did not persist following adjustment for baseline TMT-B performance.

Conclusion

In this sample of community-dwelling men, sleep microarchitecture was not independently associated with visual attention, processing speed, or executive function after 8 years.

Effect of simultaneous exercise and cognitive training on executive functions, baroreflex sensitivity, and pre-frontal cortex oxygenation in healthy older adults: a pilot study

Aging is characterized by cognitive decline affecting daily functioning. To manage this socio-economic challenge, several non-pharmacological methods such as physical, cognitive, and combined training are proposed. Although there is an important interest in this subject, the literature is still heterogeneous. The superiority of simultaneous training compared to passive control and physical training alone seems clear but very few studies compared simultaneous training to cognitive training alone. The aim of this pilot study was to investigate the effect of simultaneous exercise and cognitive training on several cognitive domains in healthy older adults, in comparison with either training alone. Thirty-five healthy older adults were randomized into one of three experimental groups: exercise training, cognitive training, and simultaneous exercise and cognitive training. The protocol involved two 30-min sessions per week for 24 weeks. Cognitive performance in several domains, pre-frontal cortex oxygenation, and baroreflex sensitivity were assessed before and after the intervention. All groups improved executive performance, including flexibility or working memory. We found a group by time interaction for inhibition cost (F_(2,28) = 6.44; p < 0.01) and baroreflex sensitivity during controlled breathing (F_(2,25) = 4.22; p = 0.01), the magnitude of improvement of each variable being associated (r = -0.39; p = 0.03). We also found a decrease in left and right pre-frontal cortex oxygenation in all groups during the trail making test B. A simultaneous exercise and cognitive training are more efficient than either training alone to improve executive function and baroreflex sensitivity. The results of this study may have important clinical repercussions by allowing to optimize the interventions designed to maintain the physical and cognitive health of older adults.

Cardiac autonomic function and cognitive performance in patients with atrial fibrillation

Background

Atrial fibrillation (AF) is associated with loss of cognition and dementia. Cardiac autonomic dysfunction has been linked to cognitive decline. We aimed to investigate if reduced cardiac autonomic function (CAF) is associated with cognitive impairment in AF patients.

Methods

Patients with paroxysmal, persistent and permanent AF were enrolled from a multicenter cohort study if they had AF (“AF group”) or sinus rhythm (“SR group”) on a baseline 5 min ECG recording. Parameters quantifying CAF (heart rate variability triangular index (HRVI), mean heart rate (MHR), RMSSD, SDNN, total power and power in the VLF, LF, HF ranges) were calculated. We used the Montreal Cognitive Assessment (MoCA) to assess global cognitive function.

Results

1685 AF patients with a mean age of 73 ± 8 years, 29% females, were included. MoCA score was 24.5 ± 3.2 in the AF group (N = 710 patients) and 25.4 ± 3.2 in the SR group (N = 975 patients). After adjusting for multiple confounders, lower HRVI was associated with lower MoCA scores, both in the SR group [β = 0.049; 95% confidence interval (CI) 0.016–0.081; p = 0.003] and in the AF group (β = 0.068; 95% CI 0.020–0.116; p = 0.006). In the AF group, higher MHR was associated with a poorer performance in the MoCA (β =  − 0.008; 95% CI − 0.014 to − 0.002; p = 0.014). We found no convincing evidence of association for other CAF parameters with cognition.

Conclusion

Our data suggest that impaired CAF is associated with worse cognitive performance in patients with AF. Among standard HRV parameters, HRVI might be the most promising ECG index.

Trial registration

ClinicalTrials.gov Identifier: NCT02105844.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00392-021-01900-4.

Baroreceptor Modulation of the Cardiovascular System, Pain, Consciousness, and Cognition

Baroreceptors are mechanosensitive elements of the peripheral nervous system that maintain cardiovascular homeostasis by coordinating the responses to external and internal environmental stressors. While it is well known that carotid and cardiopulmonary baroreceptors modulate sympathetic vasomotor and parasympathetic cardiac neural autonomic drive, to avoid excessive fluctuations in vascular tone and maintain intravascular volume, there is increasing recognition that baroreceptors also modulate a wide range of non-cardiovascular physiological responses via projections from the nucleus of the solitary tract to regions of the central nervous system, including the spinal cord. These projections regulate pain perception, sleep, consciousness, and cognition. In this article, we summarize the physiology of baroreceptor pathways and responses to baroreceptor activation with an emphasis on the mechanisms influencing cardiovascular function, pain perception, consciousness, and cognition. Understanding baroreceptor-mediated effects on cardiac and extra-cardiac autonomic activities will further our understanding of the pathophysiology of multiple common clinical conditions, such as chronic pain, disorders of consciousness (e.g., abnormalities in sleep-wake), and cognitive impairment, which may result in the identification and implementation of novel treatment modalities. © 2021 American Physiological Society. Compr Physiol 11:1373-1423, 2021.

Chemotherapy and Radiation-Associated Cardiac Autonomic Dysfunction

PURPOSE OF REVIEW

Cardiovascular autonomic dysfunction (AD) among cancer survivors is increasingly being recognized. However, the mechanisms and incidence are poorly understood. In this review, the clinical features, diagnostic modalities, proposed mechanisms, and currently available treatments of cardiovascular AD in cancer survivors are described.

RECENT FINDINGS

Much of our current understanding of cardiovascular AD is based on disease states such as diabetes, multisystem atrophy, and Parkinson's disease. Several non-invasive tests, measurements, and scoring systems have been developed as surrogates for autonomic function, with some even demonstrating associations with all-cause mortality. The mechanism of cardiovascular AD specifically in the cancer population, however, has not been directly studied. The etiology of cardiovascular AD in cancer survivors is likely multifactorial, and proposed mechanisms include direct nerve damage by chemoradiation, the pro-inflammatory state associated with malignancy, and paraneoplastic syndromes. It may also be that cardiovascular AD is an early marker of global cardiomyopathy rather than its own condition. Current pharmacologic options for cardiovascular AD are extrapolated from how it has been treated in other disease processes, and these agents have not been studied in the cancer population or compared head-to-head. Cardiovascular AD in cancer survivors can cause significant debilitation and may be associated with all-cause mortality. Current diagnostic modalities have several limitations, such as standardization and validity. However, given the nonspecific nature of cardiovascular AD, these tools provide an objective marker for diagnosis and tracking treatment response. While the mechanism of cardiovascular AD in cancer survivors has not been directly studied, it may be useful to evoke mechanisms of cardiovascular AD in other disease states such as diabetes, Parkinson's disease, and multisystem atrophy in addition to identifying unique conditions associated with malignancy like a pro-inflammatory state. Until further studies are performed, management of cardiovascular AD as seen in other disease states may serve as a guide for symptom management in cancer survivors.

Association of Heart Rate Variability With Cognitive Performance: The Multi-Ethnic Study of Atherosclerosis

Background Heart rate variability (HRV) is associated with vascular risk factors for dementia, but whether HRV is associated with specific domains of cognitive performance is unclear. Methods and Results In the Multi-Ethnic Study of Atherosclerosis (N=3018; mean age 59.3±9.2 years), we assessed the relationship of 10-second HRV to scores on tests of global cognitive performance (Cognitive Abilities Screening Instrument), processing speed (Digit Symbol Coding), and working memory (Digit Span). HRV was computed as the SD of normal-normal intervals (SDNN) and root mean square of successive differences (RMSSD) at Exam 1 (2000-2002) and Exam 5 (2010-2012). Cognitive tests were administered at Exam 5. We report regression coefficients (β [95% CI]) representing cognitive test score change per 2-fold increase in HRV. After adjustment for age, race/ethnicity, sex, education, apolipoprotein E genotype, and cardiovascular risk factors and incident disease, higher Exam 1 (β=0.37 [0.06, 0.67]) and Exam 5 (β=0.31 [0.04, 0.59]) SDNN were associated with better Cognitive Abilities Screening Instrument performance. Higher Exam 1 (β=0.80 [0.17, 1.43]) and Exam 5 (β=0.63 [0.06, 1.20]) SDNN, and Exam 5 RMSSD (β=0.54 [0.01, 1.08]) were associated with better Digit Symbol Coding performance. Finally, higher Exam 5 SDNN was associated with better Digit Span performance (β=0.17 [0.01, 0.33]). Associations were attenuated after adjustment for resting heart rate. Conclusions Higher HRV is generally associated with better cognitive performance in this multi-ethnic cohort of aging adults, and further study of the relationship of autonomic function to cognition is warranted.

Multimodal Monitoring of Cardiovascular Responses to Postural Changes

Background

In the poorly understood relationship between orthostatic hypotension and falls, next to blood pressure (BP), baroreflex sensitivity (BRS) and cerebral autoregulation (CAR) may be key measures. The posture- and movement dependency of orthostatic hypotension requires continuous and unobtrusive monitoring. This may be possible using simultaneous photoplethysmography (PPG), electrocardiography (ECG), and near-infrared spectroscopy (NIRS) signal recordings, from which pulse wave velocity (PWV; potentially useful for BP estimation), BRS and CAR can be derived. The PPG, NIRS and PWV signal correlation with BP and BRS/CAR reliability and validity need to be addressed.

Methods

In 34 healthy adults (mean age 25 years, inter quartile range 22–45; 10 female), wrist and finger PPG, ECG, bifrontal NIRS (oxygenated and deoxygenated hemoglobin) and continuous BP were recorded during sit to stand and supine to stand movements. Sixteen participants performed slow and rapid supine to stand movements; eighteen other participants performed a 1-min squat movement. Pulse wave velocity (PWV) was defined as the inverse of the ECG R-peak to PPG pulse delay; PPG, NIRS and PWV signal correlation with BP as their Pearson correlations with mean arterial pressure (MAP) within 30 s after the postural changes; BRS as inter beat interval drop divided by systolic BP (SBP) drop during the postural changes; CAR as oxygenated hemoglobin drop divided by MAP drop. BRS and CAR were separately computed using measured and estimated (linear regression) BP. BRS/CAR reliability was defined by the intra class correlation between repeats of the same postural change; validity as the Pearson correlation between BRS/CAR values based on measured and estimated BP.

Results

The highest correlation with MAP was found for finger PPG and oxygenated hemoglobin, ranging from 0.75–0.79 (sit to stand), 0.66–0.88 (supine to stand), and 0.82–0.94 (1-min squat). BRS and CAR reliability was highest during the different supine to stand movements, ranging from 0.17 – 0.49 (BRS) and 0.42-0.75 (CAR); validity was highest during rapid supine to stand movements, 0.54 and 0.79 respectively.

Conclusion

PPG-ECG-NIRS recordings showed high correlation with BP and enabled computation of reliable and valid BRS and CAR estimates, suggesting their potential for continuous unobtrusive monitoring of orthostatic hypotension key measures.

Royal Jelly Ameliorates Behavioral Deficits, Cholinergic System Deficiency, and Autonomic Nervous Dysfunction in Ovariectomized Cholesterol-Fed Rabbits

Estrogen deficiency after menopause is associated with autonomic nervous changes, leading to memory impairment and increased susceptibility to Alzheimer's disease (AD). Royal jelly (RJ) from honeybees (Apis mellifera) has estrogenic activity. Here, we investigated whether RJ can improve behavior, cholinergic and autonomic nervous function in ovariectomized (OVX) cholesterol-fed rabbits. OVX rabbits on high-cholesterol diet were administered with RJ for 12 weeks. The results showed that RJ could significantly improve the behavioral deficits of OVX cholesterol-fed rabbits and image structure of the brain. RJ reduced body weight, blood lipid, as well as the levels of amyloid-beta (Aβ), acetylcholinesterase (AchE), and malonaldehyde (MDA) in the brain. Moreover, RJ also increased the activities of choline acetyltransferase (ChAT) and superoxide dismutase (SOD) in the brain, and enhanced heart rate variability (HRV) and Baroreflex sensitivity (BRS) in OVX cholesterol-fed rabbits. Furthermore, RJ was also shown to reduce the content of Evans blue and the expression levels of Aβ, beta-site APP cleaving enzyme 1(BACE1), and receptor for advanced glycation end products (RAGE), and increase the expression level of LDL(low density lipoprotein) receptor-related protein 1 (LRP-1) in the brain. Our findings suggested that RJ has beneficial effects in neurological disorders of postmenopausal women, which were associated with reducing cholesterol and Aβ deposition, enhancing the estrogen levels and the activities of cholinergic and antioxidant systems, and ameliorating the blood⁻brain barrier (BBB) permeability and restoring autonomic nervous system.

Cerebral Aβ40 and systemic hypertension

Mid-life hypertension and cerebral hypoperfusion may be preclinical abnormalities in people who later develop Alzheimer's disease. Although accumulation of amyloid-beta (Aβ) is characteristic of Alzheimer's disease and is associated with upregulation of the vasoconstrictor peptide endothelin-1 within the brain, it is unclear how this affects systemic arterial pressure. We have investigated whether infusion of Aβ₄₀ into ventricular cerebrospinal fluid modulates blood pressure in the Dahl salt-sensitive rat. The Dahl salt-sensitive rat develops hypertension if given a high-salt diet. Intracerebroventricular infusion of Aβ induced a progressive rise in blood pressure in rats with pre-existing hypertension produced by a high-salt diet ( p < 0.0001), but no change in blood pressure in normotensive rats. The elevation in arterial pressure in high-salt rats was associated with an increase in low frequency spectral density in systolic blood pressure, suggesting autonomic imbalance, and reduced cardiac baroreflex gain. Our results demonstrate the potential for intracerebral Aβ to exacerbate hypertension, through modulation of autonomic activity. Present findings raise the possibility that mid-life hypertension in people who subsequently develop Alzheimer's disease may in some cases be a physiological response to reduced cerebral perfusion complicating the accumulation of Aβ within the brain.

Attention-deficit/hyperactivity disorder, joint hypermobility-related disorders and pain: expanding body-mind connections to the developmental age

Attention-deficit/hyperactivity disorder (ADHD) and generalized joint hypermobility (JH) are two separated conditions, assessed, and managed by different specialists without overlapping interests. Recently, some researchers highlighted an unexpected association between these two clinical entities. This happens in a scenario of increasing awareness on the protean detrimental effects that congenital anomalies of the connective tissue may have on human health and development. To review pertinent literature to identify possible connections between ADHD and GJH, special emphasis was put on musculoskeletal pain and syndromic presentations of GJH, particularly the hypermobile Ehlers-Danlos syndrome. A comprehensive search of scientific databases and references lists was conducted, encompassing publications based on qualitative and quantitative research. Impaired coordination and proprioception, fatigue, chronic pain, and dysautonomia are identified as potential bridges between ADHD and JH. Based on these findings, a map of the pathophysiological and psychopathological pathways connecting both conditions is proposed. Although ADHD and JH are traditionally separated human attributes, their association may testify for the dyadic nature of mind-body connections during critical periods of post-natal development. Such a mixed picture has potentially important consequences in terms of disability and deserves more clinical and research attention.

Long-lasting active lifestyle and successful cognitive aging in a healthy elderly population: The PROOF cohort

OBJECTIVES

The aim of this study was to determine whether cognitive reserve in the elderly affects the evolution of cognitive performance and what its relationship is with active lifestyles in later life.

METHODS

Cognitive performance was evaluated at baseline and 8 years later in 543 participants of the PROOF cohort, initially aged 67 years. Subjects were categorized as Cognitively Elite (CE), Cognitively Normal (CN) or Cognitively Impaired (CI) at each evaluation. At follow-up, demographic data and lifestyle, including social, intellectual and physical behaviors, were collected by questionnaires.

RESULTS

As much as 69% (n=375) remained unchanged, while 25.5% (n=138) decreased and 5.5% (n=30) improved. When present, the reduction in cognitive status was most often limited to one level, but was dependent on the initial level, affecting up to 73% of the initially CN, but only 58% of the initially CE. Cognitive stability was significantly associated with the degree of social engagement at follow-up (CE: P=0.009; CN: P=0.025).

CONCLUSION

In the healthy elderly, high cognitive ability predicts both cognitive ability and social involvement in later life. Cognitive decline by only one level may also extend the time to reach impairment, underlining the importance of the so-called cognitive reserve.

Potential Interactions between the Autonomic Nervous System and Higher Level Functions in Neurological and Neuropsychiatric Conditions

The autonomic nervous system (ANS) maintains the internal homeostasis by continuously interacting with other brain structures. Its failure is commonly observed in many neurological and neuropsychiatric disorders, including neurodegenerative and vascular brain diseases, spinal cord injury, and peripheral neuropathies. Despite the different underlying pathophysiological mechanisms, ANS failure associates with various forms of higher level dysfunctions, and may also negatively impact on patients’ clinical outcome. In this review, we will discuss potential relationships between ANS and higher level dysfunctions in a selection of neurological and neuropsychiatric disorders. In particular, we will focus on the effect of a documented fall in blood pressure fulfilling the criteria for orthostatic hypotension and/or autonomic-reflex impairment on cognitive performances. Some evidence supports the hypothesis that cardiovascular autonomic failure may play a negative prognostic role in most neurological disorders. Despite a clear causal relationship between ANS involvement and higher level dysfunctions that is still controversial, this might have implications for neuro-rehabilitation strategies aimed at improving patients’ clinical outcome.

Association between cardiovagal baroreflex sensitivity and baseline cerebral perfusion of the hippocampus

PURPOSE

A failure to control perfusion pressure due to impaired baroreflex sensitivity (BRS) could potentially cause chronic brain hypoperfusion, leading to cognitive dysfunction. The primary aim of this study was to determine whether BRS was associated with regional cerebral blood flow as measured by MRI arterial spin labeling (ASL) technique.

METHODS

Baroreflex sensitivity was measured using the Valsalva maneuver technique in 52 middle-aged normotensive adults (49 ± 1 years), and phase IV of the Valsalva maneuver was used for analyses. Cerebral perfusion was measured using the ASL MRI technique in 10 pre-determined brain regions of interest.

RESULTS

Hippocampal perfusion was correlated with BRS (R (2) = 0.17, P = 0.01). No association was observed between BRS and cerebral perfusion in the other brain regions of interest. Partial correlational analyses revealed that BRS was an important predictor of hippocampal perfusion, explaining 11 % of the variability independent of other covariates. When participants were divided into tertiles of BRS (11.8 ± 1.9 and 3.5 ± 0.1 ms/mmHg for the highest and lowest tertiles), regional cerebral perfusion of the hippocampus was significantly lower in the lowest BRS tertile than in the highest tertile (39.1 ± 4.3 and 60.5 ± 8.4 ml/100 g/min).

CONCLUSIONS

Baroreflex sensitivity in midlife is positively associated with regional cerebral perfusion of the hippocampus, and impaired BRS appears to be related to brain hypoperfusion even in apparently healthy middle-aged adults. Future longitudinal studies based on the present cross-sectional findings may help to further define the relationship between BRS to cognitive dysfunction.

Eight-year parallel change in baroreflex sensitivity and memory function in a sample of healthy older adults

OBJECTIVES

To examine whether changes in the cardiac autonomic nervous system (ANS) over time, as expressed by baroreflex sensitivity (BRS), were associated with long-term changes in cognitive performance in elderly individuals without dementia.

DESIGN

Community-based 8-year longitudinal study.

SETTING

Clinical settings.

PARTICIPANTS

Individuals aged 66.9 ± 0.9 (N = 425).

MEASUREMENTS

At baseline and follow-up, subjects underwent a clinical interview, autonomic and vascular measurements, and a neuropsychological evaluation including attentional, executive, and memory tests using standardized Z-scores. BRS was defined as being normal, moderate, or severe alteration at each evaluation. On the basis of the longitudinal changes subjects were stratified as being stable, moderate or improved.

RESULTS

Mean attentional, executive, and memory change Z-scores were -0.41 ± 0.9, -0.15 ± 0.7, and -0.14 ± 0.8, respectively. BRS of 56% of the subjects remained unchanged, of 20% decreased, and of 24% improved. After regression analysis, the worsened BRS group was 1.88 times as likely to have greater memory change as the group with stable BRS (P = .02). No significant association was found between longitudinal change in BRS and attentional and executive changes.

CONCLUSION

In healthy elderly individuals, BRS decrease was associated with a weak but significant decrease in memory function. The long-term effect of BRS on memory changes may suggest a role of the ANS in cognitive decline.

Sleep breathing disorders and cognitive function in the elderly: an 8-year follow-up study. the proof-synapse cohort

STUDY OBJECTIVES

Sleep breathing disorder (SBD) may be an important factor in age-related cognitive decline. In a cohort of healthy elderly subjects, we performed an 8-y longitudinal study to assess whether changes in cognitive function occur in untreated elderly patients with SBD and without dementia and the factors implicated in these changes.

DESIGN

A population-based longitudinal study.

SETTING

Clinical research settings.

PARTICIPANTS

A total of 559 participants of the PROOF study aged 67 y at the study entry and free from neurological disorders were examined.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Abnormal breathing events were defined by an apnea-hypopnea index (AHI) > 15. The raw cognitive data and averaged Z-scores for the attentional, executive, and memory functions were collected at the baseline and follow-up. At baseline, AHI > 15 was found in 54% of subjects with 18% having an AHI > 30. At follow-up, the presence of abnormal breathing events was associated with a slight but significant decline in the attentional domain (P = 0.01), which was more evident in the subjects with an AHI > 30 (P = 0.004). No significant changes over time were observed in the executive and memory functions. Several indices of chronic hypoxemia, defined either as a cumulative peripheral oxygen saturation (SpO2) < 90% or a minimal SpO2, accounted for portions of the variance in the decline in attention. All observed effects were small, accounting for 4-7% of variance in multivariate models.

CONCLUSION

In healthy elderly subjects, various components of sleep breathing disorder at baseline were associated with small changes in selected cognitive functions specific to the attention domain after controlling for multiple comorbidities, such as sleepiness, hypertension, diabetes, anxiety, and depression.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifiers NCT 00759304 and NCT 00766584.