Autism & Dementia (3):

Similarities and differences in conceptualisation, diagnosis and research

Similarities: ASD and Alzheimer’s disease (AD) are neurodevelopmental and neurodegenerative conditions that manifest themselves at different stages of life (two opposite ends of life span, i.e., childhood and old age) (Nadeem et al. 2021; Khan et al. 2016; Rhodus et al. 2020). According to the present trend, they both can be described as neurodivergent conditions. In fact, include both ASD and dementia into ‘being differently-abled’ category, alongside with knee replacement surgery, spinal cord injury, diabetes, stroke, mobility impairments, visual impairments, older adults, hearing impairments and cognitive impairments (Muthu P et al. 2023).

Like people with ASD, patients with dementia have both strengths and weaknesses. Like individuals with ASD, no two people with dementia are exactly alike (if you know one person with Alzheimer’s, you know one person with Alzheimer…), i.e., what works for one, may not be beneficial for the other.

And although Alzheimer's disease (AD) and (ASD) are etiologically distinct disorders/conditions, they share common behavioural features, including social communication difficulties, cognitive alterations, emotional problems, motor and sensory issues, etc.

However, though the symptoms of ASD may be the same as those of dementia, the root cause(s) of autism and dementia may differ as do the treatments for both.

Here we have a problem: the diagnosis of ASD is based on behaviours (which are similar to those of AD).

Diagnosis

Diagnostic strategies for ASD and dementia are different.

Dementia

It’s important to remember that dementia is NOT a diagnosis, it is an umbrella term, covering about 85 to 90 different conditions, including:

Alzheimer’s Disease (early/young onset and late onset) – 50% to 60% of all dementias; Lewy Body Dementia, Vascular Dementia, Fronto-Temporal Dementia, Semantic Dementia, Parkinson’s related, MS related; Atypical dementias: Chronic Traumatic Encephalopathy, Posterior Cortical Atrophy, Huntington’s Chorea & other genetic syndromes, Alcohol-related dementia, Progressive Supranuclear Palsy, Creutzfeldt-Jacobs disease, Battens disease, Multi-System Atrophy, White matter diseases and others.

All dementias are progressive, but each dementia has its own pattern and its own cause.

However, there are also pseudodementias, ie, conditions that resemble dementias, but in fact they are short-term (though very acute) problems, and they are treatable, for example, delirium caused by certain medication, or dehydration, or depression, or hearing/ visual problems and some others.

ASD

There is a consensus that ASD is extremely heterogeneous clinically and genetically. In fact, ASDs comprise many complex and clinically distinct neurodevelopmental disorders/conditions with both genetic and environmental components. The diagnosis of ASD, however, is based on social communication and social interaction impairments, and restricted, repetitive patterns of behaviour with three levels of severity.

“There has been no single cause or pathophysiology found to be unique to all those with autism, but current diagnostic criteria are linked to nearly two hundred genetic and environmental reported causes. The current DSM-5 criteria for an autism spectrum diagnosis allow hundreds of varied patterns of persistent deficits in social communication and social interaction, and myriad patterns of restricted and repetitive activities and interests. This wide phenotypical heterogeneity –which appears to have markedly increased in the two last decades–has led many researchers to question the validity of the ASD diagnosis” (Waterhouse & Mottron 2023).

More than 4% of autistic adults develop early-onset dementia.

Both ASD and dementias are complex neurological/neurodivergent conditions that require a nuanced understanding of their unique characteristics. Understanding their complexities is crucial in providing effective care and support for individuals affected by them.