The correlation between Attention-Deficit/Hyperactivity Disorder (ADHD) in older adults and an increased susceptibility to age-related dementias, such as Alzheimer’s disease, has recently been underscored by a comprehensive investigation led by an international consortium of neuroscientists.
Under the aegis of medical physicist Jatta Berberat from the University of Geneva, this collaborative research unearthed intriguing parallels in the distribution of iron within the brains of individuals afflicted by these interconnected conditions. Such findings may elucidate the underlying mechanisms linking these disorders.
Substantial empirical evidence indicates that as the human brain matures, there is a progressive accumulation of iron not only in the neocortex, which constitutes approximately 90 percent of the cerebral cortex, but also in subcortical regions, including the hippocampus, cerebellum, amygdala, and basal ganglia, which lie beneath the cortex.
“Elevated iron concentrations in specific cerebral regions are frequently concomitant with neurodegenerative diseases and are associated with heightened oxidative stress, which exacerbates neuronal degeneration,” elucidates psychiatrist Paul Unschuld from Geneva University Hospitals.
Excessive iron accumulation in these areas has been correlated with a decline in cognitive function. Numerous studies reveal pronounced levels of brain iron in individuals with neurodegenerative disorders, such as Huntington’s, Parkinson’s, and Alzheimer’s diseases, all of which can be readily detected using MRI technology due to their magnetic properties.
The research team utilized this imaging modality to meticulously chart the distribution of accumulated iron in the brains of 32 adults with ADHD compared to 29 neurotypical controls.
In conjunction with neuroimaging, blood samples were procured to evaluate neurofilament light chain (NfL) levels—a protein indicative of neuronal axonal damage, and a prospective biomarker for dementia. Study participants additionally completed questionnaires regarding their ADHD symptoms and lifestyle factors.
Each aspect of this modest study was deliberately designed to discern potential patterns characteristic of ADHD-related alterations in cerebral iron distribution and investigate their association with neuronal degeneration as signified by elevated NfL levels. Notably, MRI results revealed that ADHD individuals exhibited a distinctive iron distribution profile, particularly marked by augmented levels in the precentral cortex and other critical regions.
This iron topology was sufficiently divergent from that of non-ADHD individuals to warrant significant distinction.
Moreover, a statistically significant correlation was found between heightened iron concentrations in the precentral cortex of ADHD participants and their NfL blood levels. This correlation may imply that the deposition of iron in this cerebral region disrupts neurochemical communication, compromising its regulatory functions over bodily movements.
Among the ADHD cohort, 19 participants were receiving pharmacological treatment, such as methylphenidate (Ritalin) or dexamphetamine.
Some theorists posit that the long-term administration of such psychostimulant medications might underpin the observed link between ADHD and dementia risk, akin to the effects of recreational stimulant drugs like MDMA and cocaine, which have been shown to influence brain iron levels. Conversely, inquiries suggest that ADHD medications may normalize cerebral iron concentrations, albeit the ramifications of prolonged use remain insufficiently elucidated.
Regrettably, the scope of this study is too limited (and was not explicitly designed) to ascertain whether ADHD medications play an active role in this intricate web of associations or merely serve as passive participants.
Nevertheless, Unschuld expresses optimism that these findings could catalyze the development of targeted strategies aimed at mitigating dementia risk among individuals diagnosed with ADHD in their later years.
“This pursuit is particularly salient, given the established connections between lifestyle factors and modulated iron levels in the brain,” he emphasizes.
“To substantiate these initial findings, further longitudinal investigations are imperative to determine whether attenuating cerebral iron concentrations may represent a viable therapeutic avenue for dementia prevention in individuals with ADHD as they age.”
Vocabulary List:
- Correlation /ˌkɔːrəˈleɪʃən/ (noun): A mutual relationship or connection between two or more things.
- Empirical /ɪmˈpɪrɪkəl/ (adjective): Based on observation or experience rather than theory or pure logic.
- Augmented /ɔːɡˈmɛntɪd/ (adjective): Made greater or enhanced in size amount or degree.
- Neurodegenerative /ˌnjʊəroʊdɪˈdʒɛnərətɪv/ (adjective): Relating to the progressive degeneration of the structure and function of the nervous system.
- Elucidate /ɪˈluːsɪdeɪt/ (verb): To make something clear or to explain.
- Cohort /ˈkoʊhɔːrt/ (noun): A group of individuals sharing a common characteristic or experience often used in studies.
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