Mild Cognitive Impairment or Attention-Deficit/Hyperactivity Disorder in Older Adults? A Cross Sectional Study

Impact of the polygenic risk scores for attention-deficit/hyperactivity disorder in Alzheimer's disease

INTRODUCTION

Epidemiological studies indicate a link between attention-deficit/hyperactivity disorder (ADHD) and elevated risk of dementia. However, the impact of ADHD on cognition and Alzheimer's disease (AD) biomarkers in individuals with cognitive impairment remains unclear.

METHODS

We computed weighted ADHD polygenic risk scores (ADHD-PRS) in 938 cognitively impaired participants (674 mild cognitive impairment [MCI] and 264 dementia; mean age 73.5 years). A subset underwent cerebrospinal fluid (CSF) analysis for amyloid beta (Aβ) and phosphorylated tau, as well as fluorodeoxyglucose positron emission tomography ([18F]FDG-PET).

RESULTS

We observed lower executive function in individuals with high ADHD-PRS for both MCI and dementia participants. Higher levels of CSF phosphorylated tau, but not Aβ, were observed in dementia participants with higher ADHD-PRS. Increased ADHD-PRS was associated with glucose hypometabolism in the frontal and parietal cortices.

DISCUSSION

ADHD-PRS is associated with a more severe disease presentation in individuals with cognitive impairment due to dementia, characterized by impaired executive function, elevated tau pathology, and hypometabolism in the frontal and parietal cortices.

HIGHLIGHTS

We calculated the genetic liability for attention-deficit/hyperactivity disorder (ADHD) using polygenic risk scores (ADHD-PRS). Elevated ADHD-PRS was associated with executive function deficits in individuals with mild cognitive impairment (MCI) or Alzheimer's disease (AD) dementia. Higher levels of cerebrospinal fluid (CSF) phosphorylated tau, but not amyloid beta (Aβ), were observed in dementia participants with higher ADHD-PRS. Higher ADHD-PRS was associated with brain hypometabolism in individuals with AD dementia. Hypometabolism in the parietal cortex mediated the effects of ADHD-PRS on executive function.

Identifying reversible psychiatric dementia mimics in new memory clinic outpatients

Background

Timely identification of reversible conditions that mimic dementia is critical in memory clinic practice. However, psychiatric conditions as potential dementia mimics have not been studied as thoroughly as neurological ones, and detailed data on their reversibility remain limited.

Objective

To identify reversible psychiatric dementia mimics.

Methods

A retrospective chart review was conducted on 749 new outpatients to investigate etiologies, progression rates, a neuropsychological assessment, cognitive and functional levels, and potential reversibility, categorized by psychiatric and neurological conditions. Cases showing cognitive reversibility following treatment were also identified. Comparisons were made based on the presence or absence of potential reversibility, as well as actual reversibility.

Results

Among the 749 individuals, 121 (16.2%) had potentially reversible conditions: 75 psychiatric and 46 neurological. Psychiatric conditions included depression, schizophrenia and delusional disorders, developmental disorders, alcohol use disorder, and dissociative and anxiety disorders. Compared to individuals without potentially reversible conditions, individuals with psychiatric conditions were younger, had a faster progression rate, and demonstrated higher cognitive function. Of the individuals who had mild cognitive impairment or dementia mimic, 6 (0.9%) showed complete cognitive resolution (3 cases) or partial cognitive improvement (3 cases). These 6 cases included two individuals with psychiatric conditions manifesting psychotic features.

Conclusions

While rare, reversible psychiatric dementia mimics highlight the importance of comprehensive evaluations in memory clinics, particularly for younger individuals experiencing rapid cognitive decline. The infrequency of reversibility may reflect a strong association between these potentially reversible conditions and dementia risk factors, or their role as prodromes of dementia itself.

Attention-Deficit/Hyperactivity Disorder as a Potential Risk Factor for Dementia and Other Neurocognitive Disorders: A Systematic Review

Background

Attention-deficit/hyperactivity disorder (ADHD), a common neurodevelopmental condition now recognized to persist into older adulthood, has been postulated to be a risk factor for neurocognitive disorders given the overlap in clinical features and neurobiology, as well as the complex interplay between ADHD and known risk factors for dementia. Studies have emerged assessing this relationship, but there has not yet been a comprehensive systematic review addressing this topic.

Objective

To assess whether ADHD is a risk factor for neurocognitive disorders and to explore possible mechanisms for such an association.

Methods

A systematic review of the literature was conducted using Medline, Embase, and PsycINFO from inception until June 4, 2023. Studies were included if they assessed whether or how ADHD may be a risk factor for neurocognitive disorders. Studies were excluded if they were not primary literature, not published in a peer-reviewed journal, not in English, and/or used non-human subjects. Study quality was assessed using the QualSyst tool.

Results

Sixteen studies met inclusion criteria. Seven studies found a positive association between ADHD and neurocognitive disorders (all-cause dementia in four studies, Alzheimer's disease in three studies, Lewy body dementia in two studies, and mild cognitive impairment in one study). Four studies did not find an association. Five studies pertained to possible mechanisms for an association, including genetics, with minimal significant findings.

Conclusions

ADHD may be a risk factor for certain neurocognitive disorders, although the evidence base is limited, and the absolute risk is small. Possible explanations include genetic and lifestyle factors.

[Epidemiology, diagnostics and treatment of attention deficit-hyperactivity disorder (ADHD) in advanced age]

Current studies demonstrate a comparably high prevalence of attention deficit-hyperactivity disorder (ADHD) in advanced age. Older people affected by ADHD suffer from a severe burden of psychiatric and somatic comorbidities as well as substantial impairment of social functioning and subjective well-being. The diagnostic differentiation from neurodegenerative diseases is particularly difficult in this age group. This narrative review summarizes the current knowledge about the epidemiology of ADHD in advanced age and possible relationships between ADHD and the risk for neurodegeneration. Furthermore, recommendations for diagnostics and treatment options of ADHD in advanced age are presented.

Predictors of probable attention deficit hyperactivity disorder in elderly patients with mild cognitive impairment visiting a memory clinic

Aim

Characteristics of attention deficit hyperactivity disorder (ADHD) that persist into old age are often confused with symptoms of mild cognitive impairment (MCI), and the actual rate of probable ADHD in people with MCI is unknown. This study estimated the proportion of MCI patients with probable ADHD and investigated the factors to identify MCI patients with probable ADHD.

Methods

We recruited 36 elderly patients (11 males, 25 females, mean age 72.4 ± 7.6 years) who met the MCI criteria. The MCI patients were classified as those with [MCI/ADHD (+)] and without [MCI/ADHD (-)] probable ADHD, according to the Wender Utah Rating Scale scores. The autism features, inattention, and hyperactivity features during childhood and current periods, estimated intelligence quotient, and demographic data were compared between the groups. Multiple logistic regression analysis was performed to identify factors of MCI/ADHD (+) patients.

Results

Nine (25.0%) and 27 patients were added into the MCI/ADHD (+) and MCI/ADHD (-) groups, respectively. The MCI/ADHD (+) group mostly comprised men, those who visited the clinic at a younger age, had more years of schooling, and had strong autism spectrum disorder tendencies. Multiple logistic regression analysis indicated male sex and current hyperactivity as significant predictors of probable ADHD in MCI patients.

Conclusion

A quarter of the patients with MCI had probable ADHD. Male sex and hyperactivity at the time of MCI diagnosis might help in predicting probable ADHD in MCI patients. However, these results were obtained from a single-center, small-case study and should be confirmed via longitudinal studies with a large number of cases.

Annual Research Review: Perspectives on progress in ADHD science - from characterization to cause

The science of attention-deficit/hyperactivity disorder (ADHD) is motivated by a translational goal - the discovery and exploitation of knowledge about the nature of ADHD to the benefit of those individuals whose lives it affects. Over the past fifty years, scientific research has made enormous strides in characterizing the ADHD condition and in understanding its correlates and causes. However, the translation of these scientific insights into clinical benefits has been limited. In this review, we provide a selective and focused survey of the scientific field of ADHD, providing our personal perspectives on what constitutes the scientific consensus, important new leads to be highlighted, and the key outstanding questions to be addressed going forward. We cover two broad domains - clinical characterization and, risk factors, causal processes and neuro-biological pathways. Part one focuses on the developmental course of ADHD, co-occurring characteristics and conditions, and the functional impact of living with ADHD - including impairment, quality of life, and stigma. In part two, we explore genetic and environmental influences and putative mediating brain processes. In the final section, we reflect on the future of the ADHD construct in the light of cross-cutting scientific themes and recent conceptual reformulations that cast ADHD traits as part of a broader spectrum of neurodivergence.

Genetic risk for attention-deficit/hyperactivity disorder predicts cognitive decline and development of Alzheimer's disease pathophysiology in cognitively unimpaired older adults

Attention-deficit/hyperactivity disorder (ADHD) persists in older age and is postulated as a risk factor for cognitive impairment and Alzheimer's Disease (AD). However, these findings rely primarily on electronic health records and can present biased estimates of disease prevalence. An obstacle to investigating age-related cognitive decline in ADHD is the absence of large-scale studies following patients with ADHD into older age. Alternatively, this study aimed to determine whether genetic liability for ADHD, as measured by a well-validated ADHD polygenic risk score (ADHD-PRS), is associated with cognitive decline and the development of AD pathophysiology in cognitively unimpaired (CU) older adults. We calculated a weighted ADHD-PRS in 212 CU individuals without a clinical diagnosis of ADHD (55-90 years). These individuals had baseline amyloid-β (Aβ) positron emission tomography, longitudinal cerebrospinal fluid (CSF) phosphorylated tau at threonine 181 (p-tau181), magnetic resonance imaging, and cognitive assessments for up to 6 years. Linear mixed-effects models were used to test the association of ADHD-PRS with cognition and AD biomarkers. Higher ADHD-PRS was associated with greater cognitive decline over 6 years. The combined effect between high ADHD-PRS and brain Aβ deposition on cognitive deterioration was more significant than each individually. Additionally, higher ADHD-PRS was associated with increased CSF p-tau181 levels and frontoparietal atrophy in CU Aβ-positive individuals. Our results suggest that genetic liability for ADHD is associated with cognitive deterioration and the development of AD pathophysiology. Findings were mostly observed in Aβ-positive individuals, suggesting that the genetic liability for ADHD increases susceptibility to the harmful effects of Aβ pathology.

A comprehensive review of attention tests: can we assess what we exactly do not understand?

Attention, as it is now defined as a process matching data from the environment to the needs of the organism, is one of the main aspects of human cognitive processes. There are several aspects to attention including tonic alertness (a process of intrinsic arousal that varies by minutes to hours), phasic alertness (a process that causes a quick change in attention as a result of a brief stimulus), selective attention (a process differentiating multiple stimuli), and sustained attention (a process maintaining persistence of response and continuous effort over an extended period). Attention dysfunction is associated with multiple disorders; therefore, there has been much effort in assessing attention and its domains, resulting in a battery of tests evaluating one or several attentional domains; instances of which are the Stroop color-word test, Test of Everyday Attention, Wisconsin Card Sorting Test, and Cambridge Neuropsychological Test Automated Battery. These tests vary in terms of utilities, range of age, and domains. The role of attention in human life and the importance of assessing it merits an inclusive review of the efforts made to assess attention and the resulting tests; Here we highlight all the necessary data regarding neurophysiological tests which assess human attentive function and investigates the evolution of attention tests over time. Also, the ways of assessing the attention in untestable patients who have difficulty in reading or using a computer, along with the lack of ability to comprehend verbal instructions and executive tasks, are discussed. This review can be of help as a platform for designing new studies to researchers who are interested in working on attention and conditions causing deficits in this aspect of body function, by collecting and organizing information on its assessment.

From attention-deficit hyperactivity disorder to sporadic Alzheimer's disease-Wnt/mTOR pathways hypothesis

Alzheimer's disease (AD) is the most common neurodegenerative disorder with the majority of patients classified as sporadic AD (sAD), in which etiopathogenesis remains unresolved. Though sAD is argued to be a polygenic disorder, apolipoprotein E (APOE) ε4, was found three decades ago to pose the strongest genetic risk for sAD. Currently, the only clinically approved disease-modifying drugs for AD are aducanumab (Aduhelm) and lecanemab (Leqembi). All other AD treatment options are purely symptomatic with modest benefits. Similarly, attention-deficit hyperactivity disorder (ADHD), is one of the most common neurodevelopmental mental disorders in children and adolescents, acknowledged to persist in adulthood in over 60% of the patients. Moreover, for ADHD whose etiopathogenesis is not completely understood, a large proportion of patients respond well to treatment (first-line psychostimulants, e.g., methylphenidate/MPH), however, no disease-modifying therapy exists. Interestingly, cognitive impairments, executive, and memory deficits seem to be common in ADHD, but also in early stages of mild cognitive impairment (MCI), and dementia, including sAD. Therefore, one of many hypotheses is that ADHD and sAD might have similar origins or that they intercalate with one another, as shown recently that ADHD may be considered a risk factor for sAD. Intriguingly, several overlaps have been shown between the two disorders, e.g., inflammatory activation, oxidative stress, glucose and insulin pathways, wingless-INT/mammalian target of rapamycin (Wnt/mTOR) signaling, and altered lipid metabolism. Indeed, Wnt/mTOR activities were found to be modified by MPH in several ADHD studies. Wnt/mTOR was also found to play a role in sAD and in animal models of the disorder. Moreover, MPH treatment in the MCI phase was shown to be successful for apathy including some improvement in cognition, according to a recent meta-analysis. In several AD animal models, ADHD-like behavioral phenotypes have been observed indicating a possible interconnection between ADHD and AD. In this concept paper, we will discuss the various evidence in human and animal models supporting the hypothesis in which ADHD might increase the risk for sAD, with common involvement of the Wnt/mTOR-pathway leading to lifespan alteration at the neuronal levels.