Attention-deficit/hyperactivity disorder as a risk factor for dementia and mild cognitive impairment: a population-based register study

Adult Attention Deficit-Hyperactivity Disorder is associated with Lewy Body Disease and Cognitive Impairment: A prospective cohort Study With 15-year Follow-Up

OBJECTIVES

Past reports have suggested that attention-deficit/hyperactivity disorder (ADHD) may be a risk factor for Lewy body disease (LBD). To confirm this relationship, we conducted the present study.

DESIGN

A prospective observational cohort study with a follow-up to 15 years.

SETTING

The subjects were recruited from cognitive neurology clinics, where they attended for a cognitive complaint or health check-up.

PARTICIPANTS

Two groups of subjects: ADHD adults and healthy subjects.

MEASUREMENTS

The risk of dementia and LBD was estimated with Kaplan-Meier analysis comparing for the presence or absence of ADHD with the log-rank test. Predictors of conversion were assessed through separate univariate and multivariate Cox regression analyses, adjusting for several variables.

RESULTS

The baseline sample consisted of 161 subjects with ADHD and 109 without ADHD. At the end of the follow-up, 31 subjects developed dementia, 27 cases in the ADHD group and 4 in comparison group. Dementia with Lewy bodies (DLB) was the most frequent type (N:20) of which 19 corresponded to the ADHD group. The incidence of non-amnestic-MCI in the ADHD group was higher representing 67.1 % of these subjects (N:108), and 17.4% (N:19) of healthy cases. The hazard ratios for dementia and LBD in the multivariate adjusted model were 3.33 (95% CI 1.0915 to 10.1699) and 54.54 (95% CI 7.4849 to 397.5028), respectively in the ADHD group.

CONCLUSIONS

This study showed that adult ADHD is independently associated with an increased risk of LBD, dementia, and na-MCI. Future studies should clarify this relationship to develop preventive measures for these patients.

Risk of neurodegenerative disease or dementia in adults with attention-deficit/hyperactivity disorder: a systematic review

Purpose of review

Several psychiatric disorders have been associated with an increased risk of developing a neurodegenerative disease and/or dementia. Attention-deficit/hyperactivity disorder (ADHD), a neurodevelopmental disorder, has been understudied in relation to dementia risk. We summarized existing literature investigating the risk of incident neurodegenerative disease or dementia associated with ADHD.

Recent findings

We searched five databases for cohort, case-control, and clinical trial studies investigating associations between ADHD and neurodegenerative diseases/dementia in May 2023. Study characteristics were extracted by two independent raters, and risk of bias was assessed using the Newcastle Ottawa Scale. Search terms yielded 2,137 articles, and seven studies (five cohort and two case-control studies) ultimately met inclusion criteria. Studies examined the following types of neurodegeneration: all-cause dementia, Alzheimer's disease, Parkinson's and Lewy body diseases, vascular dementia, and mild cognitive impairment. Heterogeneity in study methodology, particularly covariates used in analyses and types of ratios for risk reported, prevented a meta-analysis and data were therefore summarized as a narrative synthesis. The majority of studies (4/7) demonstrated an overall low risk of bias.

Summary

The current literature on risk of developing a neurodegenerative disease in ADHD is limited. Although the studies identified present evidence for a link between ADHD and subsequent development of dementia, the magnitude of the direct effect of ADHD on neurodegeneration is yet to be determined and better empirically designed studies are first needed. Furthermore, the mechanism of how or why ADHD is associated with an increased risk of developing a neurocognitive disorder is still unclear and should be explored in future studies.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022348976, the PROSPERO number is CRD42022348976.

The diagnosis and treatment of attention-deficit hyperactivity disorder (ADHD) in older adults

INTRODUCTION

There is a striking knowledge gap on ADHD in older adults, and the diagnosis as well as treatment for ADHD in this age group.

AREAS COVERED

The authors first review the literature on the prevalence, functional impairment, and health comorbidities of ADHD across the lifespan. Next, they address the diagnostic criteria for ADHD in adults according to the DSM/ICD, available screening/diagnostic tools, differential diagnosis, and the validity of diagnostic criteria for ADHD in older adults. Finally, the authors focus on empirical evidence on the prevalence rates, medication response, and safety of pharmacological treatment of ADHD in older adults, and national and international clinical guidelines on the treatment of ADHD in this age group.

EXPERT OPINION

It is expected that future editions of the DSM and ICD will provide specifiers to the standard ADHD criteria, to better inform the diagnosis of ADHD in older adults. It is also expected that the increasing number of epidemiological studies will provide rigorous estimates on the prevalence, incidence, and burden of ADHD in older adults. One may expect an increasing number of RCTs assessing the efficacy/effectiveness and tolerability/safety of pharmacological as well as non-pharmacological interventions which will inform future guidelines on ADHD in older adults.

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.

Predicting childhood and adolescent attention-deficit/hyperactivity disorder onset: a nationwide deep learning approach

Attention-deficit/hyperactivity disorder (ADHD) is a heterogeneous disorder with a high degree of psychiatric and physical comorbidity, which complicates its diagnosis in childhood and adolescence. We analyzed registry data from 238,696 persons born and living in Sweden between 1995 and 1999. Several machine learning techniques were used to assess the ability of registry data to inform the diagnosis of ADHD in childhood and adolescence: logistic regression, random Forest, gradient boosting, XGBoost, penalized logistic regression, deep neural network (DNN), and ensemble models. The best fitting model was the DNN, achieving an area under the receiver operating characteristic curve of 0.75, 95% CI (0.74-0.76) and balanced accuracy of 0.69. At the 0.45 probability threshold, sensitivity was 71.66% and specificity was 65.0%. There was an overall agreement in the feature importance among all models (τ > .5). The top 5 features contributing to classification were having a parent with criminal convictions, male sex, having a relative with ADHD, number of academic subjects failed, and speech/learning disabilities. A DNN model predicting childhood and adolescent ADHD trained exclusively on Swedish register data achieved good discrimination. If replicated and validated in an external sample, and proven to be cost-effective, this model could be used to alert clinicians to individuals who ought to be screened for ADHD and to aid clinicians' decision-making with the goal of decreasing misdiagnoses. Further research is needed to validate results in different populations and to incorporate new predictors.

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.