At a psychological level, Alzheimer’s disease (the most common form of dementia) and Autism Spectrum Disorder both have a number of features in common. These features include catatonic state, disrupted sleep, attention transition issues and difficulty with balance and language comprehension.
However, to better understand the similarities between ASD and dementia in young people, we first need to understand the symptoms that are evident in both.
Autism Spectrum Disorder
Autism spectrum disorder (ASD) is the name given to a group of developmental disorders that include a wide range of symptoms and levels of disability. People who are autistic generally have these characteristics:
- Social problems which include difficulty in interacting with others.
- Limited interests or activities as well as repetitive behaviors.
- Symptoms that hurt a person’s ability to function at various areas of life such as socially, at school, or at work.
Mostly, ASD symptoms are recognized in the first two years of life. Some people are mildly impaired, whereas, others are severely disabled. 1 in 68 children in America are diagnosed with some form of ASD, according to the Centers for Disease Control and Prevention (CDC).
Dementia is not a specific disease, rather a wide range of conditions can cause dementia, of which Alzheimer’s is the most common. Types of dementia include mixed dementia, vascular dementia, and lewy body dementia.
Those who have dementia exhibit at least two impaired brain functions, such as impaired judgment and memory loss. Some of the most common symptoms of dementia include memory loss, difficulty in communicating and planning, struggling with complex tasks, loss of motor functions, personality changes, inappropriate behavior, paranoia, hallucinations and lack of reasoning.
A myth about dementia, however, is that only seniors develop it. Although it is more common amongst elderly people, cases have been reported where individuals as young as 30 have developed dementia. For example, brain trauma caused by a head injury could also cause dementia.
Since there are many possible causes of dementia, individuals who are affected with it have varying ages. Hence, the answer to the common question ‘Is dementia hereditary?’ is not yet established as dementia can be caused by various factors.
Definition and incidence of ‘young people’ with dementia
Since the bulk of the population that has dementia is elderly, that is people above the age of 65, the definition of ‘young onset’ of dementia does not mean children, teenagers or young adults are prone to developing it. Instead, ‘young onset’ of dementia suggests that people of a working age, usually between 30 and 65 years old have higher chances of having it. No wonder, it is also referred to as ‘working-age’ dementia and ‘early-onset’ dementia.
In the UK, it is estimated that there were 42,325 people with early-onset dementia as per the 2nd edition of Dementia UK by Alzheimer’s Society in 2014. They represent about 5% of the population that has dementia, however, because of all the difficulties of diagnosing this condition, this figure could be closer to 6-9%.
Dementia that affects younger people can be rare and hard to recognize because young individuals are very reluctant to accept that there is anything wrong with them, when they are otherwise healthy.
Therefore, they may put off going to a doctor. People with early-onset dementia are likely to be diagnosed with its rarer forms and have higher chances of having a genetically inherited form of it.
Though all forms of dementia are not hereditary, research suggests that there is a high prevalence of inherited dementias in younger-age groups. Thus, In about 10% of all people with early-onset dementia, the condition seems to be inherited from a parent.
Twins and family studies suggest that some people also have a genetic disposition towards ASD. In studies with identical twins, if one is affected then the other one also has between 36% to 95% of chances of being affected as well. Hence, in families with one autistic child, the risk of having a second child with the disorder also increases. This suggests that ASD may, to some extent, be hereditary.
People with a learning disability, such as Down syndrome, are at a greater risk of developing dementia at a younger age. One in 50 people with Down syndrome develop Alzheimer’s disease between the age of 30 to 39, one in ten aged 40 to 49, and one in three people with Down’s syndrome will have Alzheimer’s in their 50s.
Similar to early-onset dementia, an increasing number of children with Down syndrome are being diagnosed with Autism. Studies suggest that 16-19% children having Down syndrome also have ASD and 8-9% have Autism (the higher end of symptoms of ASD).
Studies conducted on neuropsychiatric and neurodevelopmental disorders have indicated that there is a genetic overlapping between Autism and Alzheimer’s disease. Patients of both have significantly similar abnormal findings in their brain including extreme deposition of metal ions such as mercury, existence of viral or bacterial infections, reduced Acetylcholine (neurotransmitter) and an increase in ß-amyloid (1-42).
Though caused by divergent mechanisms, there are many genes common to both Autism and Alzheimer’s disease, which include Fragile X mental retardation protein (FMRP), catechol-O-methyltransferase (involved in degradation of catecholamines such as dopamine, epinephrine, and norepinephrine), major histocompatibility complex, class I, A (HLA-A), Phosphatase and tensin homolog (PTEN), and Solute carrier family 6 member (SLC6A4, neurotransmitter transporter, serotonin).
Epilepsy is a neurological disorder. In an epileptic episode, certain brain nerve fire abnormally and cause effects that the person experiencing the episode has no control over. However, the type of epilepsy that most people are familiar with is one where the individual loses consciousness, falls to the floor and experiences uncontrolled convulsions.
Other symptoms of epilepsy include loss of consciousness with only minor muscle effects, partial seizures where only part of the body is affected and the individual remains conscious during the episode; seizures during sleep and twitches such as that of the eyes or eyelids. Some people also experience unusual smells or experience fear or anxiety.
Epilepsy is more common in individuals with ASD than it is in the general population. However, the overlap works both ways, which means that people with ASD are more likely to have epilepsy and people with epilepsy have higher chances of having ASD. Children whose language skills regress (a symptom of ASD) before age 3 appear to have a risk of developing epilepsy. Similarly, about 20 to 30% of children with ASD develop epilepsy, by the time they reach adulthood.
Likewise, epilepsy is more common in cases of dementia than in the general population. A UK based study found that 11.8% of patients with epilepsy, above the age of 64, also had a comorbid diagnosis of dementia. This type of dementia was significantly higher than the 1.9% comorbidity rate in the non-epilepsy older group. A Canadian study also found higher incidence of dementia in patients with epilepsy.
Autism and dementia share a lot of common attributes including lethargy, loss of intellectual abilities, sensory overload, judgement issues, difficulty with language and comprehension. People with either or both ailments can give little or no response to stimuli or need more time to respond.
On the other hand, similarities between early-onset of dementia and ASD include the possible hereditary nature of both. The higher likelihood of early-onset of dementia and/or Autism in patients with Down syndrome is also another common factor. Genetics and epilepsy play a possibly significant role in ASD as well as dementia.
Autism, Alzheimer’s, Parkinson’s, depression, memory loss and other neurological dysfunctions are a reflection of poor brain functions. Thus, addressing issues like adequate oxygen delivery, inflammation, blood sugar, hormonal imbalance, cerebrospinal fluid flow, and neurotransmitter imbalances can have profound effects on brain functions and alleviate some of the symptoms of these disorders and diseases.