Table 1.
Clinical studies on parkinsonism in autism spectrum disorders.
| Study | Design | Population | Sample size | Criteria for ASD diagnosis | Method of parkinsonism assessment | Age, years | Female, N (%) | Quality a |
|---|---|---|---|---|---|---|---|---|
| Croen et al, 2015 b | Case–control | Adults with ASD | 1507/15,070 | ICD‐9 codes in the electronic medical record system of Kaiser Permanente in Northern California | 29 + 12.2/29.4 + 12.1 | 405 (26.9%)/4050 (26.9%) | 10/10 | |
| FitzGerald et al, 1990 | Cross‐sectional | Rett syndrome | 32 | Motor‐behavioral assessment scale and assessment of ≥2 videotapes | Assessment of ≥1 videotape over 2‐year follow‐up | Range 30 months to 28 years | 32 (100%) | 8/9 |
| Geurts et al, 2022 | Cross‐sectional | ASD adults without suspected intellectual disability |
Netherlands sample: 296 US sample: 209 |
DSM‐4 or DSM‐5 | Parkinsonism Screening Questionnaire (parkinsonism defined as ≥7) |
Netherlands sample: 58.4 + 5.9 US sample: 59.35 + 7.15 |
Netherlands sample: 113 (38%) US sample: 109 (52%) |
9/9 |
| Hand et al, 2020 b | Case–control | Older adults (ages ≥65 years) with ASD | 4685/46,850 | ICD‐10 codes from Medicare Standard Analytic Files |
65–69 years 2,442 (52.1%)/24,420 (52.1%) 70–74 years 1190 (25.4%)/11,900 (25.4%) ≥75 years 1053 (22.5%)/10,530 (22.5%) |
1510 (32.2%)/15,100 (32.2%) | 10/10 | |
| Humphreys and Barrowman, 2016 | Cross‐sectional | Rett syndrome | 51 | Standardized historical questionnaire and neurologic examination | Rett Syndrome Rigidity Distribution score c | Range 2 years 5 months to 54 years | 51 (100%) | 8/9 |
| Mostert‐Kerckhoffs et al, 2020 b | Case–control | Children and adolescents with ASD |
6–12 years: 22/22 13–26 years: 23/26 |
ADI‐R and ADOS | UPDRS and mechanical assessment |
6–12 years: 10.4 + 1.7/10.3 + 1.8 13–26 years: 18.7 + 4.6/20.2 + 4.1 |
6–12 years: 5 (22.7%)/5 (22.7%) 13–26 years: 6 (26.1%)/6 (23.1%) |
8/10 |
| Starkstein et al, 2015 d | Cross‐sectional | Adults with autism |
Study 1: 19 Study 2: 37 |
DSM‐5, ADI‐R, and ADOS | UPDRS and MDS‐UPDRS |
Study 1: 57 + 6.7 Study 2: 51.2 + 8.5 |
Study 1: 0 Study 2: 5 (13.5%) |
8/9 |
| Young et al, 2020 | Cross‐sectional | Rett syndrome | 14 | Revised diagnostic criteria by Neul et al | Videotapes assessed by ≥2 independent assessors | 9.2 + 5.4 | 14 (100%) | 8/9 |
ADI‐R, Autism Diagnostic Interview‐Revised; ADOS, Autism Diagnostic Observation Schedule; ASD, autism spectrum disorders; DSM, Diagnostic and Statistical Manual of Mental Disorders; ICD, International Classification of Diseases; MDS, Movement Disorder Society; UPDRS, Unified Parkinson's Disease Rating Scale; US, United States.
The quality of cross‐sectional studies was assessed using the Joanna Briggs Institute's Checklist for Prevalence Studies (rated out of 9 points), and case–control studies using the Checklist for Case–Control Studies (rated out of 10 points).
Relevant variables (i.e., sample size, age, and proportion of females) were reported as cases/controls for these case–control studies.
The Rett Syndrome Rigidity Distribution score is an investigator‐developed survey evaluating the extent of rigidity in Rett syndrome.
The authors first conducted a hypothesis‐generating pilot study of 19 adults with ASD, followed by a second study of 37 individuals with ASD to confirm their findings.