People with Autism at a 4-Times Greater Risk of Parkinson Disease

A large population-based cohort study from Sweden has identified a significantly increased risk of Parkinson disease (PD) in individuals diagnosed with autism spectrum disorder (ASD), which may suggest a possible shared etiology. The study, published in JAMA Neurology, found that individuals with ASD had an over 4-times higher risk of developing PD compared with those without ASD, independent of known confounding factors such as antidepressant use or antipsychotic exposure. These findings add to ongoing efforts to better understand long-term neurologic outcomes in neurodevelopmental conditions like ASD.

The researchers used data from the Swedish National Patient Register to conduct a prospective cohort analysis of over 2.27 million individuals born between 1974 and 1999 who had follow-up data beginning at age 20 and continuing through 2022. The main exposure was diagnosis of ASD, while the primary outcome measured was first-ever diagnosis of PD or other degenerative parkinsonian disorder. Covariates included sex, socioeconomic status, family history of mental illness and PD, and use of antidepressants or antipsychotics. Adjusted relative risk (RR) estimates were derived using Poisson regression.

In terms of key findings:

• Among 51,954 individuals with ASD, 24 were diagnosed with PD (0.05%; 3.9 cases/100 000 person-years).
• Among 2,226,611 individuals without ASD, there were 438 with a diagnosis of PD (0.02%; 1.3 cases/100 000 person-years).
• The adjusted RR of PD in individuals with ASD was 4.43 (95% CI, 2.92 to 6.72).
• Depression and antidepressant use were associated with a greater risk of PD diagnosis independent of ASD (RR, 2.01 [95% CI, 1.40 to 2.88]).
• Antipsychotic exposure was associated with an increased risk of PD (RR, 6.35 [95% CI, 3.83 to 10.48]) and adjusting for this exposure reduced but did not attenuate the association with ASD (RR, 2.00 [95% CI, 1.27 to 3.14]).