ADHD may be linked with an increased risk of dementia

An adult brain affected by attention deficit hyperactivity disorder (ADHD) presents modifications similar to those observed in individuals suffering from dementia, suggesting that ADHD may be linked to an increased risk of developing dementia later in life. That’s according to a new study led by the Geneva University Hospitals (HUG) and the University of Geneva (UNIGE), which has been published in the journal Psychiatry and Clinical Neurosciences.

ADHD is a neurodevelopmental disorder that affects about 3.5% of adults, according to a 2008 World Health Organization (WHO) study. Old age-related dementias meanwhile affect about 55 million people globally, with Alzheimer’s disease representing 60–70% of these dementia cases.

“Recent epidemiological studies show that adults suffering from ADHD have an increased risk of dementia at an advanced age, but the mechanism through which ADHD constitutes a risk is not known,” said Professor Paul G Unschuld, Head of the Division of Geriatric Psychiatry of the HUG, Associate Professor in the Department of Psychiatry at the UNIGE Faculty of Medicine and the initiator of the new study.

The research team used an advanced brain imaging method, known as quantitative susceptibility mapping (QSM) through magnetic resonance imaging (MRI), to examine iron content in the brain of 32 adults between 25 and 45 years of age affected by ADHD and 29 healthy individuals in the same age bracket. Neurofilament light chain protein (NfL) levels in the blood of the participants were measured in parallel.

“Excess iron in certain regions of the brain is often observed and is associated with increased oxidative stress that furthers neuronal degeneration,” Unschuld explained. NfL is meanwhile an indicator of neuronal damage in the brain, with high blood levels of NfL reflecting axon damage. Consequently, increased brain iron and NfL levels may indicate an underlying neurodegenerative pathology and an increased risk of neurodegenerative dementia at old age.

The results of the study reveal notable differences in iron distribution in several regions of the brain of the individuals affected by ADHD, with more iron in certain regions when compared with neurotypical individuals. Furthermore, a significant association was established between high iron levels in the precentral cortex and high NfL levels in the blood. These results appear to confirm that a link exists between ADHD and an increased risk of dementia at old age, providing evidence for the neurological mechanism possibly involved.

The team’s discoveries pave the way for new research into understanding why people with ADHD may be at increased risk of dementia, and should enable the development of targeted prevention strategies, according to Unschuld.

“This is especially important since there is a well-known correlation between lifestyle and altered iron levels in brain,” he said. “To achieve this, additional longitudinal studies are required in order to determine if a reduction of iron levels in the brain is a potential treatment pathway for preventing dementia at an advanced age in persons with ADHD.”

The relationship between ADHD and dementia underlines the importance of early detection of these diseases. It also highlights the importance of proactive management of ADHD in adults — not only to improve quality of life, but also to prevent long-term consequences on cognitive health.

Image credit: iStock.com/SIphotography