Sensory impairment and beta-amyloid deposition in the Baltimore longitudinal study of aging

Vestibular dysfunction: a hidden risk factor for Alzheimer's disease

BACKGROUND

London taxi drivers' navigationally challenged hippocampi are known to be enlarged, and reduced Alzheimer's disease (AD)-related mortality has recently been shown in similarly well-versed drivers, implying a neuroprotective effect through hippocampal engagement. Vestibular function has been linked to hippocampal size, suggesting that vestibular input may influence AD risk.

METHODS

Including 16 known modifiable lifestyle factors as covariates, we analyzed UK Biobank (UKB) volunteers aged over 55 years and without dementia at baseline to assess how peripheral vestibular dysfunction (PVD) influences the likelihood of an AD diagnosis.

RESULTS

4684 AD and 2133 PVD cases were identified based on their ICD diagnoses; even accounting for other risk factors, PVD increased the risk of AD 1.7 times in UKB volunteers.

DISCUSSION

Vestibular loss, linked to hippocampal atrophy and default mode network disruption, appears to increase AD risk. Consequently, active vestibular stimulation by balance training or neuromodulation could offer potential for modifying AD progression.

Visual-somatosensory integration as a novel behavioral marker of amyloid pathology

INTRODUCTION

The ability to integrate information across sensory modalities is a vital aspect of everyday functioning and is linked to cognition. Increasing evidence suggests that Alzheimer's disease (AD) pathology manifests in sensory association areas before appearing in higher-order cognitive areas. We examined the role of visual-somatosensory integration (VSI) as a novel behavioral marker of AD-associated amyloid pathology.

METHODS

This cross-sectional study included 243 adults (77 ± 6.5 years; 52% female) who completed the VSI test and AD biomarker assays. The magnitude of VSI was the independent variable and amyloid-beta probability scores (APS; PrecivityADTM) were the dependent variable. Cognitive status (normal, mild cognitive impairment, or AD) was assigned during case conferences.

RESULTS

Linear regression revealed an inverse association between the magnitude of VSI and APS (β = -0.16; p ≤ 0.01). As cognitive impairment increased from normal to dementia, the magnitude of VSI decreased (p < 0.05).

DISCUSSION

Findings provide support for VSI impairment as a new behavioral marker of AD-associated amyloid pathology.

HIGHLIGHTS

Here we provide support for the magnitude of VSI as a novel behavioral marker of AD-associated amyloid pathology given its significant association with an established, accurate, and reliable biomarker of AD pathology. Adults with normal cognition maintained the highest magnitude of VSI and brain amyloid negative scores. As cognitive impairment increased, the mean magnitude of VSI significantly decreased while amyloid probability scores (APS) increased. In fact, individuals with dementia revealed the lowest magnitude of VSI and the highest APS. Our research continues to emphasize the importance of successful multisensory integration in aging, where the establishment of future novel multisensory-based interventions aimed at preventing disability and optimizing independence could prove valuable.

Dual sensory impairments in companion dogs: Prevalence and relationship to cognitive impairment

PURPOSE

Many older dogs (Canis lupus familiaris) develop cognitive impairment. Dog owners often describe impairments in multiple sensory functions, yet the relationships between sensory and cognitive function in older dogs is not well understood.

METHODS

We performed assessments of dog vision and hearing, both clinically (n = 91, electroretinography and brainstem auditory evoked potential) and via validated questionnaire (n = 238). We determined prevalence of sole and dual hearing/vision impairments in younger (<8 years) and older (≥8 years) dogs. Impairment cutoffs were determined using data from young dogs. We assessed the relationships between questionnaire-assessed vision and/or hearing impairments and cognitive impairment using logistic regression.

RESULTS

Younger and older dog groups had similar distributions of sex and purebred/mixed breed status. Sex had no relationship to prevalence of sensory impairments. Older dogs had higher prevalence of hearing, vision, and dual sensory impairments, assessed both clinically and by questionnaire (P<0.001), and cognitive impairment assessed by questionnaire (P<0.001). Dogs had higher prevalence of reported cognitive impairment when owners reported dual vision and hearing impairments (79-94%, versus 25-27% in dogs with no sensory impairments), which was most consistent in dogs aged ≥8 years. In these older dogs, dual vision/hearing impairments were associated with a significantly increased risk of cognitive impairment (1.8-2.0 odds ratio).

CONCLUSION

Dogs aged ≥8 years are at higher risk for dual hearing/vision impairments and associated cognitive impairments. The causal relationship between these impairments is not defined, but clinical consideration of these multimorbidity risks should be made in older dogs.

Effectiveness of anti-psychiatric treatment on visual and haptic perceptual disorder for a patient with Alzheimer's disease: A case report

BACKGROUND

Perception is frequently impaired in patients with Alzheimer's disease (AD). Several patients exhibit visual or haptic hallucinations.

CASE SUMMARY

A 71-year-old Chinese man presented with visual and haptic hallucinations he had been experiencing for 2 weeks. The clinical manifestations were the feeling of insects crawling and biting the limbs and geison. He looked for the insects while itching and scratching, which led to skin breakage on the limbs. He was treated with topical and anti-allergic drugs in several dermatology departments without any significant improvement. After admission, the patient was administered risperidone (0.5 mg) and duloxetine (2 mg/day). One week later, the dose of risperidone was increased to 2 mg/day, and that of duloxetine was increased to 60 mg/day. After 2 weeks of treatment, the patient's sensation of insects crawling and biting disappeared, and his mood stabilized.

CONCLUSION

This patient manifested psychiatric behavioral symptoms caused by AD brain atrophy. It was important to re-evaluate the patient's cognitive-psychological status when the patient repeatedly went to the hospital for treatment. Follow-up attention to cognitive function and the consideration of perceptual deficits as early manifestations of AD should be considered.

Vestibular dysfunction and its association with cognitive impairment and dementia

The vestibular system plays an important role in maintaining balance and posture. It also contributes to vertical perception, body awareness and spatial navigation. In addition to its sensory function, the vestibular system has direct connections to key areas responsible for higher cognitive functions, such as the prefrontal cortex, insula and hippocampus. Several studies have reported that vestibular dysfunction, in particular bilateral vestibulopathy, is associated with an increased risk of cognitive impairment and the development of dementias such as Alzheimer's disease. However, it is still controversial whether there is a causal relationship between vestibular damage and cognitive dysfunction. In this mini-review, we will explore the relationship between the vestibular system, cognitive dysfunction and dementia, hypotheses about the hypothesis and causes that may explain this phenomenon and also some potential confounders that may also lead to cognitive impairment. We will also review multimodal neuroimaging approaches that have investigated structural and functional effects on the cortico-vestibular network and finally, describe some approaches to the management of patients with vestibular damage who have shown some cognitive impairment.

Aging of the vestibular system and its relationship to dementia

PURPOSE OF REVIEW

Since October 2022, substantial new information has been published on age-related effects on the vestibular system. Since much of this evidence relates to the risk of dementia, the purpose of this review will be to provide an overview of this new information and critically evaluate it.

RECENT FINDINGS

This review will address studies published since October 2022 regarding age-related effects on the vestibular system and their relationship to cognition and dementia. There has been a particular increase in the last year in the number of studies relating aging of the vestibular system to Alzheimer's disease (AD), further supporting the view that vestibular dysfunction is associated with an increased risk of dementia.

SUMMARY

The conclusion of these recent studies is that, consistent with previous studies, vestibular function declines with age, and that this age-related decline is associated with cognitive impairment and an increased risk of dementia. Efforts are being made to consider these implications for cognition in the treatment of vestibular disorders.