In August of 2015, groups of scientists from North Carolina and Perth (Australia) published a report together in which they noted the high occurrence of Parkinson’s-like features in aging people with Autism.
In this post we will have a look at what links (if any) there may be between Autism and Parkinson’s disease.
Recent estimates suggest that the prevalence of Autistic Spectrum Disorders in US children is approximately 1.5 %. Autism is generally associated with children, and in this way it is almost a mirror opposite of Parkinson’s disease (which is usually associated with the elderly). A fair number of people who were diagnosed with Autism early in their lives are now reaching the age of retirement, but we know very little about what happens in this condition in the aged.
What is Autism?
This is one of those questions that gets people into trouble. There is a great deal of debate over how this condition should be defined/described. We here at SoPD will chose to play it safe and provide the UK National Health System (NHS)‘s description:
Autism spectrum disorder (ASD) is a condition that affects social interaction, communication, interests and behaviour. In children with ASD, the symptoms are present before three years of age, although a diagnosis can sometimes be made after the age of three. It’s estimated that about 1 in every 100 people in the UK has ASD. More boys are diagnosed with the condition than girls.
Wikipedia also has a very thorough page Autism
So what was reported in the study finding a connection between Autism and Parkinson’s disease?
Last year two groups of researchers (from North Carolina, USA and Perth, Australia) noticed an interesting trend in some of the aging Autistic subjects they were observing.
They published their findings in the Journal of Neurodevelopmental disorders:
Title: High rates of parkinsonism in adults with autism.
Authors: Starkstein S, Gellar S, Parlier M, Payne L, Piven J.
Journal: Journal of Neurodev Disord. 2015;7(1):29.
PMID: 26322138 (This report is OPEN ACCESS if you would like to read it)
The article reports the findings of two studies:
Study I (North Carolina) included 19 men with Autism (with an average age of 57 years). When the researchers investigated the cardinal features of Parkinson’s disease, they found that 22 % (N = 4) of the subjects exhibited bradykinesia (or slowness of movement), 16 % (N = 3) had a resting tremor, 32 % (N = 6) displayed rigidity, and 15 % (N = 2) had postural instability issues.
In fact, three of the 19 subjects (16 %) actually met the criteria for a full diagnosis of Parkinson’s disease (one of who was already responding well to L-dopa treatment).
Study II (Perth) was a larger study, involving 32 men and 5 women (with an average age of 51 years). 46 % (N = 17) of the subjects in this study exhibited bradykinesia, 19 % (N = 7) had a resting tremor, 19 % (N = 7) displayed rigidity, and 19 % (N = 7) had postural instability problems. In study II, 12 of the 37 subjects (32 %) met the full diagnostic criteria for Parkinson’s disease.
Given this collective result, the researchers concluded that there may well be an increased frequency of Parkinsonism in the aged people with Autism. They emphasize, however, the need to replicate the study before definitive conclusions can be made.
So how could this be happening?
The short answer is: we don’t have a clue.
The results of this study need to be replicated a few times before we can conclusively say that there is a connection. There are, however, some interesting similarities between Autism and Parkinson’s disease, for example (as the NHS mentioned above) males are more affected than females in both conditions.
There are genetic variations that both Parkinson’s and Autism share. Approximately 10-20% of people with Parkinson’s disease have a genetic variation in one of the PARK genes (we have discussed these before – click here to read that post). The genetics of Autism are less well understood. If you have one child with Autism, the risk for the next child also having the condition is only 2-6% (genetically speaking, it should be a 25-50% level of risk).
There are, however, some genes associated with Autism and one of those genes is the Parkinson’s associated gene, PARK2. it has previously been reported that variants in the PARK2 gene (Parkin) in children with Autism (click here for more on this).
It would be interesting to have a look at the brains of aged people with Autism. This could be done with brain scans (DAT-SCAN), but also at the postmortem stage to see if their brains have alpha synuclein clusters and Lewy bodies – the pathological characteristics of Parkinson’s disease. These studies may well be underway – we’ll keep an eye out for any reports.
There are alternative explanations for the connection between Autism and Parkinson’s disease suggested by this study. For example, 36 of the 56 subjects involved in the two studies were on medication for their Autism (the medication is called neuroleptics). Those medications did not appear to explain the rates of parkinsonism in either study (after excluding subjects currently on neuroleptic medications, the frequency of parkinsonism was still 20 %). Most of the subjects in both studies have been prescribed neuroleptics at some point in their lives. Thus it is possible that long-term use of neuroleptics may have had the effect of increasing the risk for parkinsonism later in life. This is pure speculation, however, and yet to be tested. Any future studies would need to investigate this as a possibility.
EDITOR’S NOTE: If you have a child or loved one on the Autism spectrum, it is important to understand that the study summarised here are novel results that are yet to be replicated. And if it turns out that adults with Autism do have a higher risk of developing Parkinson’s disease it does not necessarily mean that they will – simply that they are at greater risk than normal. It is best to consult a medical practitioner if you have further concerns.
The banner at the today’s post was sourced from Sailing Autistic Seas.