Cardiac autonomic modulation and cognitive status in Alzheimer’s disease

Abstract

The cognitive status and the cardiac sympathovagal modulation appear to be correlated and hypothetically may influence one another in mild to severe Alzheimer's disease. Individuals with more severe cognitive deficiency showed suggestive lower cardiac parasympathetic modulation and trend for higher cardiac sympathetic modulation.

Autonomic Dysfunction in Mild Cognitive Impairment: Evidence from Power Spectral Analysis of Heart Rate Variability in a Cross-Sectional Case-Control Study

“…This latter possibility is of considerable clinical interest in the quest for predictors of evolution to dementia and deserves some discussion. It is true that in the literature there is a lack of direct evidence that dysautonomia causes cognitive decline since the studies investigating HRV in dementia or MCI [16]–[22], [54] are cross-sectional and the prospective analyses from the study by Britton et al [23] reveal only a weak association between HRV at baseline and changes in cognition at follow-up. However, Britton et al focus on a population at lower risk of cognitive decline (middle-aged adults not selected for cognitive impairment) and do not carry out detailed neuropsychological testing.…”

“…In fact, given that many drugs have a presumed impact on the ANS, the approach of excluding all medications that may affect HRV (e.g. [18], [21], [22], would have yielded a sample of subjects not representative of the underlying population. On the other hand, including all medications (e.g.…”

“…We chose to analyse the last 5 minutes since 5 minutes is the time believed to be necessary for adjustment of autonomic function to posture [87] and lies at the upper range of the stabilization period adopted by most HRV studies involving orthostatic testing (e.g. [21], [22], [88]). We opted for an active rather than passive standing test because the former is more easily implemented in routine geriatric clinical practice and there is evidence that the two manoeuvres are comparable in terms of changes in autonomic balance [89]; 3) supine paced breathing at 12 breaths/min (0.2 Hz) (parasympathetic stimulation) [10]: 15 minutes during which the subjects breathed, as regularly as possible and with a “comfortable” tidal volume, according to an electronic metronome set at 24 acoustic signals per minute (2.5 s inspiration, 2.5 s expiration).…”

“…First, MCI is considered a condition of predementia and a number of studies have demonstrated an impaired autonomic function in dementia, whether by clinical autonomic tests [12]–[16] or HRV analysis [17]–[21]. Also, a recent study has shown that, within a group of patients with Alzheimer's disease (AD), there was a positive correlation between cognitive status and parasympathetic HRV indices [22]. Second, MCI is characterized by a slight cognitive impairment and several studies, although with some exception [23], have revealed a significant association between the performance on cognitive tests and HRV-derived autonomic function across different age groups and conditions.…”

Heart Rate Spectra Confirm the Presence of Autonomic Dysfunction in Dementia Patients

“…In those patients, MIBG uptake was demonstrated to be reduced [8] and plasma norepinephrine concentrations supine and standing are reduced. Parasympathetic involvement was found to be partially impaired [9] and correlated with cognitive decline [10]. In the light of high incidence of autonomic dysfunction, a closer look on autonomic modulation seems appropriate, facilitating a different technical approach than previously applied: The standard test battery for cardiovascular autonomic evaluation, the Ewing battery, provides data on sympathetic and parasympathetic dysfunction during standardized tests, by investigating the biosignals blood pressure and electrocardiogram (ECG) with linear time-series analysis [11, 12].…”