Autonomic dysfunction in patients with Alzheimer’s disease

Abstract

Objective: To look for evidence of cardiac autonomic dysfunction in patients with Alzheimer's disease (AD).Rationale: Limbic structures are important components of central autonomic control, which undergo degeneration in AD. Acetylcholine is a major neurotransmitter of parasympathetic system and there is cholinergic depletion in AD.Methods: It is a prospective two group comparative study. 25 clinically probable Alzheimer's patients were compared with 25 age and gender matched healthy controls. Short term heart rate variability (HRV), blood pressure variability (BPV) and baroreflex sensitivity (BRS) were assessed. Comparison between the groups was done using Mann-Whitney and Wilcoxon test. Spearman's correlation co-efficient was used to assess correlation between the disease severity and study parameters.Results: In Alzheimer's group, among frequency domain parameters of HRV, high frequency power in normalized units (HF nu) was significantly low (p<0.05): low frequency power in normalized units (LF nu) and LF/HF ratio was significantly high (p<0.05). There was a negative correlation between HF nu and disease severity and a positive correlation between LF nu and LF/HF ratio and disease severity.Discussion: There is a significant reduction in parasympathetic activity with sympathyovagal imbalance with sympathetic dominance in AD. This may be due to central autonomic dysfunction as well as cholinergic depletion. In addition, cardiac autonomic dysfunction and disease severity are positively correlated. Conclusion:There is statistically significant abnormality suggestive of sympathetic predominance and suppression of parasympathetic activity in AD group as compared to control group.

Autonomic nervous system dysfunction throughout menopausal transition: A potential mechanism underpinning cardiovascular and cognitive alterations during female ageing

“…Interestingly, observational studies have shown an association between CVD and AD, particularly in women (Liu et al., 2022; Volgman et al., 2019). Moreover, AD patients exhibit autonomic imbalance characterized by parasympathetic withdrawal, enhanced sympathetic tone, as evidenced by a high incidence of cardiac arrhythmias (atrial fibrillation), neurovascular dysfunction, lower heart rate variability and impaired arterial baroreflex sensitivity (Gupta et al., 2017; Ihara & Washida, 2018; Nicolini et al., 2020; Niedziela et al., 2020; Toledo & Junqueira, 2010). A recent population‐based cohort study demonstrated that elevated resting heart rate and blood pressure, hallmarks of sympathetic hyperactivation, were independently associated with incident dementia in older adults, suggesting a shared pathway between CVD and cognitive decline (Imahori et al., 2022).…”

Investigation of Autonomic Dysfunction in Alzheimer’s Disease—A Computational Model-Based Approach

“…This enzyme catalyzes the production of ACh from choline and Acetyl coenzyme A. Additionally, synaptic reuptake of choline, which is necessary for replenishing the primary acetylcholine store for succeeding rounds of neurotransmission, is decreased to 60% of normal levels in AD. According to direct testing, ACh synthesis levels are lowered by 50% in affected patients [ 2 ].…”

“…Neelesh Gupta et al have presented a study of autonomic function tests in a group of AD patients and compared the outcomes with age and gender-matched healthy volunteers [ 2 ]. Low-frequency power in normalized units (LF nu) and the LF/HF ratio (sympathovagal ratio) were both significantly higher ( p < 0.05) in the Alzheimer’s group, while high-frequency power in normalized units (HF nu) was considerably low ( p < 0.05).…”