ADHD and Age-Related Cognitive Changes: Known (and Unclear) Connections
Is ADHD a risk factor for developing mild cognitive impairment, cognitive decline, or dementia? Here, an expert sheds light on what the research has revealed — and what is still unknown.
Historically, ADHD was considered a childhood neurodevelopmental disorder. Now we know from published research that < ahref="https://www.additudemag.com/adult-adhd-symptoms-bias-stigma/">ADHD continues well into older ages. Unfortunately, many memory clinics’ assessments fail to consider pre-existing ADHD when evaluating older adults’ complaints of cognitive difficulties.
Emerging research is beginning to inquire whether the presence of ADHD in older adults is associated with neurodegenerative disorders like Parkinson’s disease, movement disorders, or dementia. Eight studies published over the past 15 years suggest that ADHD may be a risk factor for neurodegenerative conditions. These results are based on data from population registers with links to health information, healthcare utilization databases, or health insurance databases.
However, it is important to note the two major methodologic limitations to the studies: accuracy of ADHD diagnosis, in part because of poor symptom recall as a child/adolescent, and controlled sample size, or the number of older adults without ADHD. That means studies contain biases that interfere with an accurate interpretation of the findings. So, at best, these findings are preliminary, and researchers will continue to investigate.
Cognitive Changes Related to Age
Cognitive changes in older adults are subtle and may include misplacing items, spending more time looking for items, forgetting the names of people you would otherwise know, not being able to think of a word when you’re in the middle of a sentence, slow recall of information you know, stumbling over the spelling of a word you know, and difficulty holding information in your head as you make a decision. The progression of these changes should be monitored in the event they worsen to become mild cognitive deficit. There is no evidence currently that ADHD is a risk factor for accelerating the development of age-related cognitive changes. These include the following:
Mild Cognitive Impairment and ADHD
Mild cognitive impairment (MCI) is a diagnosis defined as cognitive deficits that are observable by others but that don’t cause significant impairment in daily function. There is a significant risk that MCI may evolve into dementia. ADHD in older adults may be misdiagnosed as mild cognitive impairment because the cognitive symptoms are almost indistinguishable. While it has been suggested that ADHD may be a risk factor for developing MCI, neuroimaging has demonstrated that different brain areas are involved with ADHD and MCI. The conclusion is that ADHD involves different neural networks than does MCI, and it is not a precursor for MCI.
[Read: Inside the Aging ADHD Brain]
Dementia and ADHD
When cognitive decline becomes very evident to the patient and others, and is accompanied by impairments in daily life, a diagnosis of dementia may be given. Each form of dementia—Alzheimer’s, Lewy body dementia, frontotemporal dementia, and vascular dementia—has its own unique pathology in the brain, which accounts for somewhat different clinical symptoms. Of the different types of dementias, Lewy body diseases have up to a five-fold increase when associated with ADHD.
Parkinson’s Disease and ADHD
This condition is characterized by a resting tremor in the hands, a shuffling walking pattern, cognitive decline, agitation and/or anxiety, and hallucinations when Parkinson’s is severe. Parkinson’s disease results from a loss of dopamine neurons in a specific area of the brain, the substantia nigra. Neuron loss results in a decrease of dopamine. ADHD is also considered a disorder resulting from lower dopamine, and, therefore, perhaps related. However, a study looking at the genetics of both disorders shows no relationship.
Other Movement Disorders
Beyond Parkinson’s, other movement disorders involve changes in the basal ganglion and/or the cerebellum area of the brain. While there is some relationship between ADHD and disorders from these brain areas, the relationship may be accounted for by other factors: time spent on stimulants, the severity of the ADHD, or other factors not yet recognized.
[Read: A Critical Need Ignored – Inadequate Diagnosis and Treatment of ADHD After Age 60]
Ongoing Studies of the Aging Brain
Research involving the relationship between ADHD and brain changes that lead to other neurodegenerative disorders is still in its infancy. Replication of findings is critical to accurately interpret this relationship.
While this information may be concerning and even alarming, I suggest that older patients with ADHD monitor any symptoms that may reflect cognitive decline and/or possible muscular movement disorders. If you are concerned, discuss these observations with your prescriber.
Cognitive Changes and ADHD: Next Steps
- Read: Signs of Adult ADHD? Or Old Age?
- Watch: Growing Old with ADHD – 5 Common Challenges After 60
- Read: ADHD and Alzheimer’s – Are These Diseases Related?
David W. Goodman, M.D., LFAPA, is an assistant professor in psychiatry and behavioral sciences at the Johns Hopkins School of Medicine.
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