AI-based differential diagnosis of dementia etiologies on multimodal data

Differential diagnosis of dementia remains a challenge in neurology due to symptom overlap across etiologies, yet it is crucial for formulating early, personalized management strategies. Here, we present an AI model that harnesses a broad array of data, including demographics, individual and family medical history, medication use, neuropsychological assessments, functional evaluations, and multimodal neuroimaging, to identify the etiologies contributing to dementia in individuals. The study, drawing on 51,269 participants across 9 independent, geographically diverse datasets, facilitated the identification of 10 distinct dementia etiologies. It aligns diagnoses with similar management strategies, ensuring robust predictions even with incomplete data. Our model achieved a micro-averaged area under the receiver operating characteristic curve (AUROC) of 0.94 in classifying individuals with normal cognition, mild cognitive impairment and dementia. Also, the micro-averaged AUROC was 0.96 in differentiating the dementia etiologies. Our model demonstrated proficiency in addressing mixed dementia cases, with a mean AUROC of 0.78 for two co-occurring pathologies. In a randomly selected subset of 100 cases, the AUROC of neurologist assessments augmented by our AI model exceeded neurologist-only evaluations by 26.25%. Furthermore, our model predictions aligned with biomarker evidence and its associations with different proteinopathies were substantiated through postmortem findings. Our framework has the potential to be integrated as a screening tool for dementia in various clinical settings and drug trials, with promising implications for person-level management.

Piecing it together: atrophy profiles of hippocampal subfields relate to cognitive impairment along the Alzheimer's disease spectrum

Introduction

People with Alzheimer's disease (AD) experience more rapid declines in their ability to form hippocampal-dependent memories than cognitively normal healthy adults. Degeneration of the whole hippocampal formation has previously been found to covary with declines in learning and memory, but the associations between subfield-specific hippocampal neurodegeneration and cognitive impairments are not well characterized in AD. To improve prognostic procedures, it is critical to establish in which hippocampal subfields atrophy relates to domain-specific cognitive declines among people along the AD spectrum. In this study, we examine high-resolution structural magnetic resonance imaging (MRI) of the medial temporal lobe and extensive neuropsychological data from 29 amyloid-positive people on the AD spectrum and 17 demographically-matched amyloid-negative healthy controls.

Methods

Participants completed a battery of neuropsychological exams including select tests of immediate recollection, delayed recollection, and general cognitive status (i.e., performance on the Mini-Mental State Examination [MMSE] and Montreal Cognitive Assessment [MoCA]). Hippocampal subfield volumes (CA1, CA2, CA3, dentate gyrus, and subiculum) were measured using a dedicated MRI slab sequence targeting the medial temporal lobe and used to compute distance metrics to quantify AD spectrum-specific atrophic patterns and their impact on cognitive outcomes.

Results

Our results replicate prior studies showing that CA1, dentate gyrus, and subiculum hippocampal subfield volumes were significantly reduced in AD spectrum participants compared to amyloid-negative controls, whereas CA2 and CA3 did not exhibit such patterns of atrophy. Moreover, degeneration of the subiculum along the AD spectrum was linked to a significant decline in general cognitive status measured by the MMSE, while degeneration scores of the CA1 and dentate gyrus were more widely associated with declines on the MMSE and tests of learning and memory.

Discussion

These findings provide evidence that subfield-specific patterns of hippocampal degeneration, in combination with cognitive assessments, may constitute a sensitive prognostic approach and could be used to better track disease trajectories among individuals on the AD spectrum.

Movement-related beta and gamma oscillations indicate parallels and disparities between Alzheimer's disease and HIV-associated neurocognitive disorder

People with HIV (PWH) often develop HIV-related neurological impairments known as HIV-associated neurocognitive disorder (HAND), but cognitive dysfunction in older PWH may also be due to age-related disorders such as Alzheimer's disease (AD). Discerning these two conditions is challenging since the specific neural characteristics are not well understood and limited studies have probed HAND and AD spectrum (ADS) directly. We examined the neural dynamics underlying motor processing during cognitive interference using magnetoencephalography (MEG) in 22 biomarker-confirmed patients on the ADS, 22 older participants diagnosed with HAND, and 30 healthy aging controls. MEG data were transformed into the time-frequency domain to examine movement-related oscillatory activity and the impact of cognitive interference on distinct stages of motor programming. Both cognitively impaired groups (ADS/HAND) performed significantly worse on the task (e.g., less accurate and slower reaction time) and exhibited reductions in frontal and cerebellar beta and parietal gamma activity relative to controls. Disease-specific aberrations were also detected such that those with HAND exhibited weaker gamma interference effects than those on the ADS in frontoparietal and motor areas. Additionally, temporally distinct beta interference effects were identified, with ADS participants exhibiting stronger beta interference activity in the temporal cortex during motor planning, along with weaker beta interference oscillations dispersed across frontoparietal and cerebellar cortices during movement execution relative to those with HAND. These results indicate both overlapping and distinct neurophysiological aberrations in those with ADS disorders or HAND in key motor and top-down cognitive processing regions during cognitive interference and provide new evidence for distinct neuropathology.

Sleep quality differentially modulates neural oscillations and proteinopathy in Alzheimer's disease

BACKGROUND

Alterations in resting-state neural activity have been reported in people with sleep disruptions and in patients with Alzheimer's disease, but the direct impact of sleep quality on Alzheimer's disease-related neurophysiological aberrations is unclear.

METHODS

We collected cross-sectional resting-state magnetoencephalography and extensive neuropsychological and clinical data from 38 biomarker-confirmed patients on the Alzheimer's disease spectrum and 20 cognitively normal older control participants. Sleep efficiency was quantified using the Pittsburgh Sleep Quality Index.

FINDINGS

Neural activity in the delta frequency range was differentially affected by poor sleep in patients on the Alzheimer's disease spectrum. Such neural changes were related to processing speed abilities and regional amyloid accumulation, and these associations were mediated and moderated, respectively, by sleep quality.

INTERPRETATION

Together, our results point to a mechanistic role for sleep disturbances in the widely reported neurophysiological aberrations seen in patients on the Alzheimer's disease spectrum, with implications for basic research and clinical intervention.

FUNDING

National Institutes of Health, USA.

Convergent and divergent oscillatory aberrations during visuospatial processing in HIV-related cognitive impairment and Alzheimer's disease

Adults with HIV frequently develop a form of mild cognitive impairment known as HIV-associated neurocognitive disorder (HAND), but presumably cognitive decline in older persons with HIV could also be attributable to Alzheimer's disease (AD). However, distinguishing these two conditions in individual patients is exceedingly difficult, as the distinct neural and neuropsychological features are poorly understood and most studies to date have only investigated HAND or AD spectrum (ADS) disorders in isolation. The current study examined the neural dynamics underlying visuospatial processing using magnetoencephalography (MEG) in 31 biomarker-confirmed patients on the ADS, 26 older participants who met criteria for HAND, and 31 older cognitively normal controls. MEG data were examined in the time-frequency domain, and a data-driven approach was utilized to identify the neural dynamics underlying visuospatial processing. Both clinical groups (ADS/HAND) were significantly less accurate than controls on the task and exhibited stronger prefrontal theta oscillations compared to controls. Regarding disease-specific alterations, those with HAND exhibited stronger alpha oscillations than those on the ADS in frontoparietal and temporal cortices. These results indicate both common and unique neurophysiological alterations among those with ADS disorders and HAND in regions serving visuospatial processing and suggest the underlying neuropathological features are at least partially distinct.

Oscillatory markers of neuroHIV-related cognitive impairment and Alzheimer's disease during attentional interference processing

People with HIV (PWH) frequently experience mild cognitive decline, which is typically attributed to HIV-associated neurocognitive disorder (HAND). However, such declines could also be a sign of early Alzheimer's disease (AD) in older PWH. Distinguishing these two pathologies in PWH is exceedingly difficult, as there is a major knowledge gap regarding their neural and neuropsychological bases. In the current study, we begin to address this knowledge gap by recording magnetoencephalography (MEG) during a flanker interference task in 31 biomarker-confirmed patients on the AD spectrum (ADS), 25 older participants with HAND, and 31 cognitively-normal controls. MEG data was examined in the time-frequency domain using a data-driven approach. Our results indicated that the clinical groups (ADS/HAND) performed significantly worse than controls on the task and exhibited aberrations in interference-related theta and alpha oscillations, some of which were disease-specific. Specifically, patients (ADS/HAND) exhibited weaker interference activity in frontoparietal and cingulate cortices compared to controls, while the ADS group exhibited stronger theta interference than those with HAND in frontoparietal, occipital, and temporal cortices. These results reveal overlapping and distinct patterns of neurophysiological alterations among those with ADS and HAND in attentional processing centers and suggest the existence of unique oscillatory markers of each condition.

Altered visual entrainment in patients with Alzheimer’s disease: magnetoencephalography evidence

Recent research has indicated that rhythmic visual entrainment may be useful in clearing pathological protein deposits in the central nervous system of mouse models of Alzheimer’s disease. However, visual entrainment studies in human patients with Alzheimer’s disease are rare, and as such the degree to which these patients exhibit aberrations in the neural tracking of rhythmic visual stimuli is unknown. To fill this gap, we recorded magnetoencephalography during a 15 Hz visual entrainment paradigm in amyloid-positive patients on the Alzheimer’s disease spectrum and compared their neural responses to a demographically matched group of biomarker-negative healthy controls. Magnetoencephalography data were imaged using a beamformer and virtual sensor data were extracted from the peak visual entrainment responses. Our results indicated that, relative to healthy controls, participants on the Alzheimer’s disease spectrum exhibited significantly stronger 15 Hz entrainment in primary visual cortices relative to a pre-stimulus baseline period. However, the two groups exhibited comparable absolute levels of neural entrainment, and higher absolute levels of entertainment predicted greater Mini-mental Status Examination scores, such that those patients whose absolute entrainment amplitude was closer to the level seen in controls had better cognitive function. In addition, 15 Hz periodic activity, but not aperiodic activity, during the pre-stimulus baseline period was significantly decreased in patients on the Alzheimer’s disease spectrum. This pattern of results indicates that patients on the Alzheimer’s disease spectrum exhibited increased visual entrainment to rhythmic stimuli and that this increase is likely compensatory in nature. More broadly, these results show that visual entrainment is altered in patients with Alzheimer’s disease and should be further examined in future studies, as changes in the capacity to entrain visual stimuli may prove useful as a marker of Alzheimer’s disease progression.

Signatures of somatosensory cortical dysfunction in Alzheimer's disease and HIV-associated neurocognitive disorder

Alzheimer's disease is the most common type of dementia in the general population, while HIV-associated neurocognitive disorder is the most common neurological comorbidity in those infected with HIV and affects between 40 and 70% of this population. Both conditions are associated with cognitive impairment and have been associated with aberrant functioning in sensory cortices, but far less is known about their disparate effects on neural activity. Identifying such disparate effects is important because it may provide critical data on the similarities and differences in the neuropathology underlying cognitive decline in each condition. In the current study, we utilized magnetoencephalography, extensive neuropsychological testing and a paired-pulse somatosensory gating paradigm to probe differences in somatosensory processing in participants from two ongoing magnetoencephalography studies. The resulting participant groups included 27 cognitively normal controls, 26 participants with HIV-associated neurocognitive disorder and 21 amyloid biomarker-confirmed patients with Alzheimer's disease. The data were imaged using a beamformer and voxel time series were extracted to identify the oscillatory dynamics serving somatosensory processing, as well as the amplitude of spontaneous cortical activity preceding stimulation onset. Our findings indicated that people with Alzheimer's disease and HIV-associated neurocognitive disorder exhibit normal somatosensory gating but have distinct aberrations in other elements of somatosensory cortical function. Essentially, those with Alzheimer's disease exhibited accentuated neural responses to somatosensory stimulation, along with spontaneous gamma activity preceding stimulus onset. In contrast, those with HIV-associated neurocognitive disorder exhibited normal responses to somatosensory stimulation but had sharply elevated spontaneous gamma activity prior to stimulus onset. These distinct aberrations may reflect the impact of different neuropathological mechanisms underlying each condition. Further, given the differential pattern of deficits in somatosensory cortical function, these measures may function as unique biomarkers in each condition and be useful in identifying persons with HIV who may go on to develop Alzheimer's disease.

Multimodal deep learning for Alzheimer's disease dementia assessment

Worldwide, there are nearly 10 million new cases of dementia annually, of which Alzheimer's disease (AD) is the most common. New measures are needed to improve the diagnosis of individuals with cognitive impairment due to various etiologies. Here, we report a deep learning framework that accomplishes multiple diagnostic steps in successive fashion to identify persons with normal cognition (NC), mild cognitive impairment (MCI), AD, and non-AD dementias (nADD). We demonstrate a range of models capable of accepting flexible combinations of routinely collected clinical information, including demographics, medical history, neuropsychological testing, neuroimaging, and functional assessments. We then show that these frameworks compare favorably with the diagnostic accuracy of practicing neurologists and neuroradiologists. Lastly, we apply interpretability methods in computer vision to show that disease-specific patterns detected by our models track distinct patterns of degenerative changes throughout the brain and correspond closely with the presence of neuropathological lesions on autopsy. Our work demonstrates methodologies for validating computational predictions with established standards of medical diagnosis.

Spatially resolved neural slowing predicts impairment and amyloid burden in Alzheimer's disease

An extensive electrophysiological literature has proposed a pathological ‘slowing’ of neuronal activity in patients on the Alzheimer’s disease spectrum. Supported by numerous studies reporting increases in low-frequency and decreases in high-frequency neural oscillations, this pattern has been suggested as a stable biomarker with potential clinical utility. However, no spatially resolved metric of such slowing exists, stymieing efforts to understand its relation to proteinopathy and clinical outcomes. Further, the assumption that this slowing is occurring in spatially overlapping populations of neurons has not been empirically validated.

In the current study, we collected cross-sectional resting state measures of neuronal activity using magnetoencephalography from 38 biomarker-confirmed patients on the Alzheimer’s disease spectrum and 20 cognitively normal biomarker-negative older adults. From these data, we compute and validate a new metric of spatially resolved oscillatory deviations from healthy ageing for each patient on the Alzheimer’s disease spectrum.

Using this Pathological Oscillatory Slowing Index, we show that patients on the Alzheimer’s disease spectrum exhibit robust neuronal slowing across a network of temporal, parietal, cerebellar and prefrontal cortices. This slowing effect is shown to be directly relevant to clinical outcomes, as oscillatory slowing in temporal and parietal cortices significantly predicted both general (i.e. Montreal Cognitive Assessment scores) and domain-specific (i.e. attention, language and processing speed) cognitive function. Further, regional amyloid-β accumulation, as measured by quantitative ¹⁸F florbetapir PET, robustly predicted the magnitude of this pathological neural slowing effect, and the strength of this relationship between amyloid-β burden and neural slowing also predicted attentional impairments across patients.

These findings provide empirical support for a spatially overlapping effect of oscillatory neural slowing in biomarker-confirmed patients on the Alzheimer’s disease spectrum, and link this effect to both regional proteinopathy and cognitive outcomes in a spatially resolved manner. The Pathological Oscillatory Slowing Index also represents a novel metric that is of potentially high utility across a number of clinical neuroimaging applications, as oscillatory slowing has also been extensively documented in other patient populations, most notably Parkinson’s disease, with divergent spectral and spatial features.

Somatosensory dysfunction is masked by variable cognitive deficits across patients on the Alzheimer's disease spectrum

Background

Alzheimer's disease (AD) is generally thought to spare primary sensory function; however, such interpretations have drawn from a literature that has rarely taken into account the variable cognitive declines seen in patients with AD. As these cognitive domains are now known to modulate cortical somatosensory processing, it remains possible that abnormalities in somatosensory function in patients with AD have been suppressed by neuropsychological variability in previous research.

Methods

In this study, we combine magnetoencephalographic (MEG) brain imaging during a paired-pulse somatosensory gating task with an extensive battery of neuropsychological tests to investigate the influence of cognitive variability on estimated differences in somatosensory function between biomarker-confirmed patients on the AD spectrum and cognitively-normal older adults.

Findings

We show that patients on the AD spectrum exhibit largely non-significant differences in somatosensory function when cognitive variability is not considered (p-value range: .020–.842). However, once attention and processing speed abilities are considered, robust differences in gamma-frequency somatosensory response amplitude (p < .001) and gating (p = .004) emerge, accompanied by significant statistical suppression effects.

Interpretation

These findings suggest that patients with AD exhibit insults to functional somatosensory processing in primary sensory cortices, but these effects are masked by variability in cognitive decline across individuals.

Funding

National Institutes of Health, USA; Fremont Area Alzheimer's Fund, USA

Visuospatial alpha and gamma oscillations scale with the severity of cognitive dysfunction in patients on the Alzheimer's disease spectrum

Background

Entrainment of neural oscillations in occipital cortices by external rhythmic visual stimuli has been proposed as a novel therapy for patients with Alzheimer’s disease (AD). Despite this increased interest in visual neural oscillations in AD, little is known regarding their role in AD-related cognitive impairment and in particular during visuospatial processing.

Methods

We used source-imaged magnetoencephalography (MEG) and an established visuospatial processing task to elicit multi-spectral neuronal responses in 35 biomarker-confirmed patients on the AD spectrum and 20 biomarker-negative older adults. Neuronal oscillatory responses were imaged to the level of the cortex, and group classifications and neurocognitive relationships were modeled using logistic and linear regression, respectively.

Results

Visuospatial neuronal oscillations in the theta, alpha, and gamma ranges significantly predicted the classification of patients on the AD spectrum. Importantly, the direction of these effects differed by response frequency, such that patients on the AD spectrum exhibited weaker alpha-frequency responses in lateral occipital regions, and stronger gamma-frequency responses in the primary visual cortex, as compared to biomarker-negative older adults. In addition, alpha and gamma, but not theta, oscillations robustly predicted cognitive status (i.e., MoCA and MMSE scores), such that patients with neural responses that deviated more from those of healthy older adults exhibited poorer cognitive performance.

Conclusions

We find that the multi-spectral neural dynamics supporting visuospatial processing differentiate patients on the AD spectrum from cognitively normal, biomarker-negative older adults. Oscillations in the alpha and gamma bands also relate to cognitive status in ways that are informative for emerging clinical interventions.

Spatio-spectral relationships between pathological neural dynamics and cognitive impairment along the Alzheimer's disease spectrum

INTRODUCTION

Numerous studies have described aberrant patterns of rhythmic neural activity in patients along the Alzheimer's disease (AD) spectrum, yet the relationships between these pathological features and cognitive decline are uncertain.

METHODS

We acquired magnetoencephalography (MEG) data from 38 amyloid-PET biomarker-confirmed patients on the AD spectrum and a comparison group of biomarker-negative cognitively normal (CN) healthy adults, alongside an extensive neuropsychological battery.

RESULTS

By modeling whole-brain rhythmic neural activity with an extensive neuropsychological profile in patients on the AD spectrum, we show that the spectral and spatial features of deviations from healthy adults in neural population-level activity inform their relevance to domain-specific neurocognitive declines.

DISCUSSION

Regional oscillatory activity represents a sensitive metric of neuronal pathology in patients on the AD spectrum. By considering not only the spatial, but also the spectral, definitions of cortical neuronal activity, we show that domain-specific cognitive declines can be better modeled in these individuals.

Screening for cognitive impairment in older adults with hematological malignancies using the Montreal Cognitive Assessment and neuropsychological testing

OBJECTIVES

The primary objective of the current study is to describe the prevalence and profile of cognitive domains affected in older adults with hematological malignancies evaluated for hematopoietic cell transplantation (HCT) using the Montreal Cognitive Assessment (MoCA) and neuropsychological tests. The secondary objective is to determine if a specific MoCA cut-off score would correlate with the identification of cognitive impairment detected by neuropsychological tests. This would facilitate interpretation of cognitive screening and referral of patients who would likely need further neuropsychological testing.

MATERIALS AND METHODS

Fifty-one patients 60 years and older who were evaluated for HCT were assessed using a battery of standardized neuropsychological tests and MoCA. We analyzed Receiver Operating Characteristics (ROC) comparing MoCA scores and four different neuropsychological test criteria for cognitive impairment.

RESULTS

The prevalence of cognitive impairment detected by neuropsychological tests was 53 to 70.6% using the criteria for patients with cancer by the International Cancer Cognition Task Force (ICCTF). The following cognitive domains were most affected: language, learning and memory, visuospatial skills, and executive function. MoCA is an appropriate screening test for cognitive impairment. Using the ICCTF criteria, 86 to 100% of patients are correctly classified as having significant cognitive impairment on neuropsychological tests using a cut-off score of 20 or less.

CONCLUSION

There is a high prevalence of cognitive impairment identified by neuropsychological tests in older patients with hematological malignancies evaluated for HCT. Identification of an appropriate MoCA cut-off score in this population is important to identify patients who would benefit from further assessment.

The Association Between Body Mass Index, and Cognitive, Functional, and Behavioral Declines for Incident Dementia

BACKGROUND

Association between high adiposity and the clinical progression of dementia remains puzzling.

OBJECTIVE

To separately examine the association between body mass index (BMI) and cognitive, functional, and behavioral declines before, at, and after diagnosis of dementia, and further stratified by age groups, and sex.

METHODS

A total of 1,141 individuals with incident dementia were identified from the Uniform Data Set of the National Alzheimer's Coordinating Center. Cognitive function was evaluated by Mini-Mental State Exam, functional abilities were assessed using Functional Activities Questionnaire, and behavioral symptoms were captured by Neuropsychiatric Inventory Questionnaire at each follow-up visit. We used separate linear-mixed effects models to examine the association.

RESULTS

Compared to moderate baseline BMI, high baseline BMI was associated with 0.30-point slower annual progression rates in functional decline. For individuals aged 76 and over, high baseline BMI was associated with 0.42-point faster progression rates in cognitive decline annually. A U-shaped association between baseline BMI and cognitive decline was observed among men.

CONCLUSION

BMI levels before dementia diagnosis may facilitate the identification of different risk profiles for progression rates of cognitive and functional declines in individuals who developed dementia.

Cerebrovascular Reactivity Impairment in Preclinical Alzheimer's Disease

BACKGROUND AND PURPOSE

A substantial overlap exists between declines in cerebral vasoreactivity (CVR) and symptomatic Alzheimer's disease (AD). CVR can be quantified using transcranial Doppler (TCD) measurement of cerebral blood flow velocities (CBFV) in the middle cerebral artery (MCA) with CO₂ as a vasodilatory stimulus. The breath-hold acceleration index (BHAI) is a new, more reliable measure of CVR developed recently in our laboratory. Our primary goal is to explore the possibility of using TCD for asymptomatic AD screening.

METHODS

A pilot study population was divided into three groups: 9 healthy control subjects, 8 subjects identified as preclinical AD, and 10 patients diagnosed with prodromal or mild AD. Control subjects had a Clinical Dementia Rating (CDR) score of 0 without elevated amyloid-β (Aβ) on amyloid positron emission tomography (PET) imaging, preclinical AD subjects had CDR = 0 with elevated Aβ, and prodromal to mild AD subjects had CDR scores ≥.5 and elevated Aβ. CVR was calculated using two indices: the conventional breath-holding index (BHI) and the new BHAI. TCD parameters between the three groups were compared.

RESULTS

BHAI was able to distinguish between 9 normal control subjects and 8 preclinical-AD subjects with high statistical significance (P < .001). BHI and pulsatility index were able only to distinguish AD from healthy and preclinical subjects (P < .001).

CONCLUSIONS

In this exploratory pilot study, CVR was significantly decreased in preclinical, prodromal, and mild AD subjects as compared to the healthy group. Lower CVR in the preclinical AD group was detected using the new BHAI index but not the conventional BHI index.

The Breath-Hold Acceleration Index: A New Method to Evaluate Cerebrovascular Reactivity using Transcranial Doppler

BACKGROUND AND PURPOSE

Cerebrovascular reactivity (CR) is an ideal biomarker to detect cerebrovascular damage. CR can be quantified by measuring changes in cerebral blood flow velocity (CBFV) resulting from a CO₂  vasodilatory stimulus, often using the breath-holding index (BHI). In this method, transcranial Doppler (TCD) ultrasound is used to measure CBFV changes in the middle cerebral artery (MCA) during a breath-hold maneuver. Despite its convenience, BHI has high variability. Changing body position may contribute to potential variability. It is important to determine if CR differs with body position. The aims of this study were, first, to propose an alternative, more robust index to evaluate CR using a breath-hold maneuver; second, investigate the effect of body position on CR measured with conventional (BHI) and a new proposed index.

METHODS

Ten healthy young volunteers held their breath for 30 seconds on a tilt table. CR was calculated at five different angles using two indices: the conventional BHI, and the breath-hold acceleration index (BHAI), a new index obtained by linear regression of the most linear portion of the mean velocity change during the breath-hold maneuver. The regression represents acceleration (change in blood flow velocity per unit of time) sampled at each cardiac cycle.

RESULTS

The mean coefficient of variation was 43.7% lower in BHAI in comparison with BHI. Neither index was statistically significant between body positions (P > .05).

CONCLUSIONS

BHAI has less variability in comparison with the conventional standard BHI. Additionally, neither index showed statistical significance in CR based on change in body position.

Hyperbaric oxygen for late sequelae of carbon monoxide poisoning enhances neurological recovery: case report

Neuropsychiatric sequelae have been reported in 15%-45% of survivors of carbon monoxide (CO) poisoning. Hyperbaric oxygen (HBO₂) therapy reduces the incidence of cognitive and neurological a dysfunction. The efficacy of providing HBO₂ beyond the first one to two days after initial insult is unknown. However, some evidence exists for the benefit of this treatment. We report on treating a patient 14 months after CO injury, who responded with markedly improved neurologic status. A 27-year-old scholar was found comatose due to CO poisoning (carboxyhemoglobin = 31.7%). He received five acute HBO₂ treatments. After discharge, he developed chorea, Parkinsonism, dystonia, memory loss, slowed processing speed and verbal fluency, leaving him disabled. After the patient reached a clinical plateau, HBO₂ was tried again at 90 minutes at 2.4 ATA plus air breaks. Neuropsychological testing was performed at baseline and after each 20 HBO₂ cycles, five of which were performed during the period from 14-22 months after CO exposure. After the first 20 treatments, Parkinsonism and dystonia improved. After 40 sessions, further improvements were seen on mental speed, verbal fluency, and fine motor movements. The outcome following 100 treatments was that the patient regained independence, including the ability to drive and to become gainfully employed. Our case calls into question the concept that HBO₂ therapy has no role during the chronic phase of CO brain injury. Randomized clinical trials should be considered to evaluate the therapeutic efficacy of HBO₂ in patients with neurological sequelae following CO injury.

The Risk of Incident Mild Cognitive Impairment and Progression to Dementia Considering Mild Cognitive Impairment Subtypes

Background

It remains unclear how demographic and clinical characteristics are related to the risk of incident mild cognitive impairment (MCI) by its subtypes. Moreover, the contribution of the subtypes of incident MCI to the progression to dementia remains puzzling.

Methods

We used data collected by the National Alzheimer Coordinating Center. Our analysis sample included cognitively normal subjects at baseline. The associations were examined using competing-risks survival regression models and Cox proportional hazards models.

Results

About 16.3% of subjects developed incident MCI of whom 15.8% progressed to Alz­heimer disease (overall mean follow-up of 4.3 years). The risk of incident amnestic MCI (aMCI) was greater in subjects with 1 copy (subhazard ratio [SHR]: 1.23; 95% CI: 1.00–1.50) or 2 copies (SHR: 2.14; 95% CI: 1.49–3.05) of the APOE ε4 allele than in those who had no ε4 allele. Multiple-domain aMCI patients were more likely to progress to dementia than single-domain aMCI patients (hazard ratio: 2.14; 95% CI: 1.28–3.58).

Conclusions

Cognitively normal subjects with an APOE ε4 allele had a higher likelihood of developing aMCI and the MCI subtype was associated with the dementia subtype. Our findings provide important information about practical indicators for the prediction of cognitive decline.

The Impact of Age on Cognition

This article reviews the cognitive changes that occur with normal aging, the structural and functional correlates of these cognitive changes, and the prevalence and cognitive effects of age-associated diseases. Understanding these age-related changes in cognition is important given our growing elderly population and the importance of cognition in maintaining functional independence and effective communication with others. The most important changes in cognition with normal aging are declines in performance on cognitive tasks that require one to quickly process or transform information to make a decision, including measures of speed of processing, working memory, and executive cognitive function. Cumulative knowledge and experiential skills are well maintained into advanced age. Structural and function changes in the brain correlate with these age-related cognitive changes, including alterations in neuronal structure without neuronal death, loss of synapses, and dysfunction of neuronal networks. Age-related diseases accelerate the rate of neuronal dysfunction, neuronal loss, and cognitive decline, with many persons developing cognitive impairments severe enough to impair their everyday functional abilities. There is emerging evidence that healthy lifestyles may decrease the rate of cognitive decline seen with aging and help delay the onset of cognitive symptoms in the setting of age-associated diseases.

Neural correlates of cognitive decline in ALS: an fNIRS study of the prefrontal cortex

Functional near infrared spectroscopy (fNIRS) is a clinically feasible functional neuroimaging modality for detecting early cortical changes due to neurodegenerative diseases that affect cognition. The objective of this preliminary investigation was to test for reduced prefrontal activity in persons with cognitive impairments due to amyotrophic lateral sclerosis (ALS). Participants were required to complete two N-back working memory tasks of increasing complexity during fNIRS recordings. Five participants with ALS and age- and gender-matched healthy participants comprised the experimental and control groups, respectively. Significant reductions in prefrontal oxygenation levels were observed for the left and right hemispheres in the ALS group compared to the control group. Reduced prefrontal activation despite intact behavioral performance for a working memory task may suggest early neuroanatomical, neurophysiological and/or compensatory mechanisms in affected individuals. The fNIRS-derived oxygenation measure shows promise as a sensitive neural marker to identify early neuropsychological impairments due to ALS.

CD4+ regulatory and effector/memory T cell subsets profile motor dysfunction in Parkinson's disease

Animal models and clinical studies have linked the innate and adaptive immune system to the pathology of Parkinson’s disease (PD). Despite such progress, the specific immune responses that influence disease progression have eluded investigators. Herein, we assessed relationships between T cell phenotype and function with PD progression. Peripheral blood lymphocytes from two separate cohorts, a discovery cohort and a validation cohort, totaling 113 PD patients and 96 age- and environment-matched caregivers were examined by flow cytometric analysis and T cell proliferation assays. Increased effector/memory T cells (Tem), defined as CD45RO+ and FAS+ CD4+ T cells and decreased CD31+ and α4β7+ CD4+ T cells were associated with progressive Unified Parkinson’s Disease Rating Scale III scores. However, no associations were seen between immune biomarkers and increased age or disease duration. Impaired abilities of regulatory T cells (Treg) from PD patients to suppress effector T cell function was observed. These data support the concept that chronic immune stimulation, notably Tem activation and Treg dysfunction is linked to PD pathobiology and disease severity, but not disease duration. The association of T cell phenotypes with motor symptoms provides fresh avenues for novel biomarkers and therapeutic designs.

Early treatment of Parkinson's disease: opportunities for managed care

The diagnosis and treatment of Parkinson's disease (PD) typically occur when the disease has already progressed to a relatively advanced stage in which motor symptoms are clearly evident and substantial neurophysiological damage has already taken place. Nonmotor symptoms, which account for a large proportion of PD symptoms, usually emerge much earlier and offer both an early indication for treatment and a therapeutic target. A growing body of data from the medical literature points to several critical advantages that may be associated with early therapeutic intervention in PD. The most evident benefit of early intervention is a reduction in symptoms, particularly dyskinesia, and the delay of levodopa initiation. Clinical trials suggest but have yet to conclusively demonstrate that early treatment can slow disease progression. Both the diminishment of symptoms and the potential for slowing disease progression have large implications for improving patient quality of life. The enormous direct costs associated with PD would also likely be reduced over the long term with earlier treatment. The great majority of costs attributable to PD occur when the disease is at its most advanced stage and when symptoms are most severe. An early-treatment strategy that diminishes symptoms and that has the potential to slow disease progression could have a meaningful impact on PD expenditures. Adherence, too, must be taken into consideration, particularly since PD patients are generally poorly adherent to prescribed therapies, especially therapies with complex dosing schedules. Taking advantage of more convenient and adherencefriendly drug formulations may further help to improve outcomes and lower costs in PD.

Progressive personality and language changes in a 62-year-old woman

A 62-year-old woman with no known psychiatric illness had a 1.5-year history of progressive personality and language changes, leading to a loss of functional independence. Laboratory results revealed elevated autoimmune antibodies. She did not improve on high-dose steroid therapy and continued to deteriorate to her death, 2.5 years after symptom onset.

Closing gaps in antiretroviral therapy access: human immunodeficiency virus-associated dementia screening instruments for non-physician healthcare workers

Human immunodeficiency virus-associated dementia (HIV-D) is an indication for antiretroviral therapy (ART), but HIV-D is not routinely screened for in ART clinics in sub-Saharan Africa. Given the dearth of physicians in sub-Saharan Africa, enabling non-physician healthcare workers to identify HIV-D is crucial for early treatment initiation and preventing chronic neurologic disability. Non-physician healthcare workers administered locally adapted screening instruments to 48 persons living with acquired immunodeficiency syndrome (PLWAs), and 15 healthy comparison persons provided normative data. Stage IV PLWAs performed worse than the comparison group on all tests. Overall, 24 (50%) of 48 PLWAs had significant cognitive impairment. Among HIV staging categories, 1 stage II (33%), 6 stage III (42%), and 17 stage IV (55%) patients were identified as cognitively impaired. Our pilot study indicates that screening instruments used by non-physician healthcare workers can identify cognitive impairment in PLWAs and may facilitate appropriate initiation of ART in resource-poor settings.

The influence of caregiver mastery on depressive symptoms

PURPOSE

The purpose of this study was to explore how the relationship between care recipients' problem behaviors and caregivers' depressive symptoms varies as a function of caregiver mastery, controlling for the effects of caregiver age, gender, and relationship to the care recipient in caregivers of people with primary malignant brain tumor (PMBT).

DESIGN

A cross-sectional design was used to gather data via telephone interviews from 95 caregivers of people with primary malignant brain tumor, recruited from 2003 to 2004 from a brain tumor treatment center, two national support groups, and a statewide cancer registry.

METHODS

Measures for the study included the Neuropsychiatric Inventory-Questionnaire, Caregiver Mastery, and the Center for Epidemiologic Studies-Depression. A stepwise regression procedure was used to evaluate potential moderating and mediating relationships.

FINDINGS

Data did not indicate that caregiver mastery was a moderating variable. The analysis showed caregiver mastery as a partial mediator, with both a direct effect of care recipients' problem behaviors on caregivers' depressive symptoms and an indirect effect through caregiver mastery. Concerning the indirect effect, care recipients' problem behaviors were related to lower levels of caregiver mastery, which in turn were related to more depressive symptoms in caregivers.

CONCLUSIONS

Findings showed a link between care recipients' problem behaviors and caregivers' depressive symptoms, a relationship that has not been well established in oncology. This association indicates one mechanism through which problem behaviors in the care recipient might lead to caregiver depressive symptoms.

Predictive validity of neuropsychiatric subgroups on nursing home placement and survival in patients with Alzheimer disease

OBJECTIVE

The aim of the study was to conceptualize neuropsychiatric symptoms in patients with Alzheimer disease as distinct symptom profiles with differential disease outcomes. Two outcomes of interest in the study were nursing home placement and survival.

METHOD

Cluster analysis was used to categorize 122 patients with Alzheimer disease based on their neuropsychiatric symptoms as assessed by the Neuropsychiatric Inventory. Both the presence as well as the severity and frequency of symptoms were considered. After identification of the subgroups, the predictive validity of the categorization was tested on time to nursing home placement and time to death over a three-year period. Cox proportional hazard models were used to perform survival analysis. Important covariates such as severity of cognitive and functional impairments, comorbid medical conditions, presence of parkinsonism, and marital status were adjusted at baseline.

RESULTS

Based on the presence of neuropsychiatric symptoms, three subgroups were identified: minimally symptomatic, highly symptomatic, and affective/apathetic. Over a three-year period, the highly symptomatic group had an increased risk of nursing home placement. In addition, the rates of survival were significantly lower for the highly symptomatic and the affective/apathetic subgroups. Based on the severity and frequency of symptoms, two-cluster and four-cluster solutions were produced. The groupings based on severity and frequency of symptoms predicted significant differential outcomes in survival and nursing home placement.

CONCLUSIONS

Neuropsychiatric subgroups were able to predict differential outcomes and identify those with an increased risk for a worse prognosis. The findings were discussed through their research and clinical implications.

Evaluated Need, Costs of Care, and Payer Perspective in Degenerative Dementia Patients Cared for in the United States

The purpose of this study was to examine the strength of the associations between 5 measures of need that are potentially modifiable in degenerative dementia patients and direct costs of care from 5 payer perspectives in the US healthcare system. Data were derived from a cohort study of 150 patients with a degenerative dementia. We measured need variables at baseline and utilization of healthcare in the year before and after baseline. Utilization data were converted into estimated direct costs and totaled based on the costs paid for by 5 payers in the US healthcare system. Path models were used to quantify and compare the relationships between need variables and direct costs. From Medicare's perspective, comorbid medical conditions were the most important predictor of Medicare costs. From Medicaid's perspective, neuropsychiatric symptoms and signs of parkinsonism were additional significant predictors. From the perspective of patients, their families and society, all 5 need variables were significant predictors of direct costs (ie, those above, plus cognitive impairment, and dependency). The relationship between evaluated need variables and direct costs depends on the perspective of the payer and provide insights into which need variables could be targeted with interventions to control costs and improve patient outcomes.

Predictors of distress in caregivers of persons with a primary malignant brain tumor

The purpose of this cross-sectional, descriptive study was to identify predictors of distress for family caregivers of persons with a primary malignant brain tumor (PMBT). The effect of the care recipient's functional, cognitive, and neuropsychiatric status on caregiver burden and depressive symptoms was examined through telephone interviews with 95 caregivers. Care recipients' neuropsychiatric status consistently affected caregivers' depressive symptoms and burden, and assisting with activities of daily living affected burden related to caregivers' schedules and health. The care recipient's cognitive status and need for assistance with instrumental activities of daily living did not affect any outcome variable. Results may help identify caregivers at risk for negative outcomes, and suggest interventions to improve caregivers' emotional health.

The economic impact of neuropsychiatric symptoms in Alzheimer's disease: can drugs ease the burden?

The majority of patients with Alzheimer's disease (AD) will have clinically significant neuropsychiatric symptoms during the course of their disease. There is growing evidence that neuropsychiatric symptoms increase direct costs of care in patients with AD, especially the costs associated with formal long-term care and unpaid caregiving. For example, we have estimated that a 1-point worsening of the neuropsychiatric inventory score is associated with an incremental increase of between USD 247 and USD 409 per year in total direct costs of care based upon year 2001 US dollars, depending on the value of unpaid caregiving. Although data are still limited, there have been a series of well designed, controlled clinical trials that have established the efficacy of several drugs used in the treatment of neuropsychiatric symptoms in patients with AD. The economic impact of using efficacious drugs to treat neuropsychiatric symptoms in patients with AD has not been evaluated formally. To successfully complete formal economic evaluations of these drugs there is a need for more research to refine methods for determining the economic value of unpaid caregiving and to collect more data concerning the incremental effects of neuropsychiatric symptoms on QOL, costs of care and survival. The current ongoing treatment trials that are collecting economic and QOL data as a part of the trial will be able to perform cost-effectiveness and cost-utility analyses of these new efficacious drugs. These economic evaluations will provide important information for decision makers who are formulating healthcare policy for the treatment of patients with AD.

Primary malignant brain tumor incidence and Medicaid enrollment

BACKGROUND

The relationship between socioeconomic status and health care disparities in the incidence of brain tumors is unclear.

OBJECTIVE

To identify the associations between age, sex, and Medicaid enrollment and the incidence of primary malignant brain tumors in Michigan in 1996 and 1997.

METHODS

Records were obtained from the Michigan Cancer Surveillance Program on the 1,006 incident cases during this period and cross-checked with Medicaid enrollment files.

RESULTS

Persons enrolled in Medicaid were more likely than non-enrolled persons to develop a malignant brain tumor of any type, a glioblastoma multiforme, and an astrocytoma for certain subgroups. In addition, incidence rates for malignant brain tumors in persons enrolled in Medicaid peaked at a younger age.

CONCLUSION

Sociodemographic status may be associated with cerebral malignancy and should be considered when targeting treatment and educational interventions at persons at risk.

The impact of parkinsonism on costs of care in patients with AD and dementia with Lewy bodies

OBJECTIVE

To compare the annual direct costs for patients with Alzheimer's disease (AD) and no parkinsonism (AD), patients with AD and parkinsonism (AD/P), and patients with dementia with Lewy bodies (DLB). For the entire sample, the authors examined the incremental costs associated with increasing parkinsonism.

METHODS

Cross-sectional comparisons of 1 year of direct costs were done. Fifteen patients met criteria for DLB, and 133 met criteria for probable AD, of whom 39 had signs of parkinsonism and 94 did not. Patients' caregivers reported on the patient's use of health care services, receipt of unpaid care, and comorbid medical conditions. Severity of cognitive impairment and parkinsonism were determined during patient examinations. Costs were estimated by multiplying utilization data by a unit cost for each type of care. Costs were compared after adjustment for covariates using multiple regression equations.

RESULTS

After adjusting for important covariates, patients with AD/P or DLB had significantly higher annual direct costs than patients with AD. The average adjusted increases in costs above the AD baseline costs were 7,119 dollars (AD/P) and 13,754 dollars (DLB) for formal direct costs and 7,394 dollars (AD/P) and 19,564 dollars (DLB) for total direct costs. Models for the entire sample estimated that a 1-point increase in a parkinsonism scale would result in an annual increase of 784 dollars in formal costs and 827 dollars in total costs of care.

CONCLUSIONS

Patients with Alzheimer's disease and parkinsonism or dementia with Lewy bodies have significantly higher formal and total direct costs of care than patients with Alzheimer's disease. Signs of parkinsonism in patients with degenerative dementias are significant independent predictors of costs of care.

The incremental direct costs associated with behavioral symptoms in AD

OBJECTIVE

To determine the incremental costs associated with behavioral symptoms in patients with AD.

METHODS

A total of 128 patients with probable AD were enrolled into this study. Cognitive function and extrapyramidal features were assessed in patients with AD. Caregivers were interviewed to determine use of health care services, receipt of unpaid care, severity of behavioral symptoms (Neuropsychiatric Inventory [NPI]), and comorbid medical conditions in patients with AD. Healthcare utilization data were multiplied by unit costs to estimate direct formal costs. Unpaid caregiving hours were multiplied by an hourly wage to estimate direct informal costs. The annual incremental direct costs of additional behavioral symptoms were estimated with multiple regression equations.

RESULTS

Annual, direct costs were significantly higher in patients with AD at or above the median score on the NPI (high NPI group), after adjusting for group differences in severity of cognitive impairment and comorbid conditions. Patients in the high NPI group had formal costs between US$3,162 and US$5,919 higher than the low NPI group and total direct costs between US$10,670 and US$16,141 higher, depending on the severity of cognitive impairments. Models for the entire sample estimated that a one-point increase in the NPI score would result in an annual increase of between US$247 and US$409 in total direct costs, depending on the value of unpaid caregiving.

CONCLUSIONS

Behavioral symptoms in patients with AD significantly increase direct costs of care.