Risk Of Parkinson's Disease 4 Times Higher In People With Autism: Study

People with autism could be four times more likely to develop Parkinson's disease later in life, according to a study among Swedish population.

Autism is a neuro-developmental disorder affecting thought processes and social behaviour. It is diagnosed in early childhood, while Parkinson's disease is ageing-related neuro-degeneration, in which one experiences tremors in limbs and affected movement.

"This indicates that there can be shared biological drivers behind ASD (autism spectrum disorder) and Parkinson's disease," first author Weiyao Yin, a researcher at the department of medical epidemiology and biostatistics, Karolinska Institutet, Sweden, said.

The study, published in The Journal of the American Medical Association (JAMA) Neurology, analysed data from more than 22 lakh people born in the country between 1974 and 1999, who were followed from the age of 20 up to the end of 2022.

Findings "suggest a potential shared etiology between neuro-developmental disorders and PD (Parkinson's disease), warranting increased awareness of long-term neurological conditions in individuals with ASD," the authors wrote.

Yin said, "One hypothesis is that the brain's dopamine system is affected in both cases, since the neurotransmitter (brain chemical) dopamine plays an important part in social behaviour and motion control." While there is considerable evidence that dopamine production is affected in Parkinson's disease, the role of dopamine in autism is not yet clear, even though studies have shown that the brain chemical is involved, the researchers said.

The researchers also took into account the fact that people diagnosed with autism are commonly prescribed anti-depressants and anti-psychotic drugs, which can cause Parkinson's-like symptoms.

The link between autism and Parkinson's disease became less pronounced, "but the risk was still double", the researchers said.

"The healthcare services need to keep people with ASD -- a vulnerable group with high co-morbidity and a high use of psychotropics -- under long-term observation," last author Sven Sandin, a statistician and epidemiologist at the department of medical epidemiology and biostatistics, Karolinska Institutet, said.

"At the same time, it's important to remember that a Parkinson's diagnosis before the age of 50 is very rare, including for people with autism," Sandin said.

The researchers pointed out that they only analysed early-onset Parkinson's disease before the age of 50 and that the average age of participants by the end of the study was 34.

The incidence of Parkinson's disease was therefore very low -- 24 cases among 51,954 people with autism (0.05 per cent), and 438 among 22,26,611 people without autism (0.02 per cent).

Future studies will need to examine if the elevated risk persists into older age, the team said.

Global estimate of autism prevalence is one per cent, while in India, the estimate is 1.5 per cent, according to a 2023 study published in the Indian Journal of Pediatrics.

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