Parkinson's Disease and Driving Fitness: A Systematic Review of the Existing Guidelines

Abstract

Background

Motor/nonmotor symptomatology and antiparkinsonian drugs deteriorate the driving ability of Parkinson's disease (PD) patients.

Objectives

Treating neurologists are frequently asked to evaluate driving fitness of their patients and provide evidence‐based consultation. Although several guidelines have been published, the exact procedure along with the neurologist's role in this procedure remains obscure.

Methods

We systematically reviewed the existing guidelines, regarding driving fitness evaluation of PD patients. We searched MEDLINE and Google Scholar and identified 109 articles. After specified inclusion criteria were applied, 15 articles were included (nine national guidelines, five recommendation papers, and one consensus statement).

Results

The treating physician is proposed as the initial evaluator in 8 of 15 articles (neurologist in 2 articles) and may refer patients for a second‐line evaluation. The evaluation should include motor, cognitive, and visual assessment (proposed in 15, 13, and 8 articles, respectively). Specific motor tests are proposed in eight articles (cutoff values in four), whereas specific neuropsychological and visual tests are proposed in seven articles each (cutoff values in four and three articles, respectively). Conditional licenses are proposed in 11 of 15 articles, to facilitate driving for PD patients. We summarized our findings on a graphic of the procedure for driving fitness evaluation of PD patients.

Conclusions

Neurological aspects of driving fitness evaluation of PD patients are recognized in most of the guidelines. Motor, neuropsychological, visual, and sleep assessment and medication review are key components. Clear‐cut instructions regarding motor, neuropsychological, and visual tests and relative cutoff values are lacking. Conditional licenses and periodical reevaluation of driving fitness are important safety measures.

Parkinson's disease (PD) is the second most common neurodegenerative disease affecting millions of people worldwide. It comprises motor symptoms (including the cardinal signs of PD: bradykinesia, rigidity, rest tremor, and postural instability) and nonmotor symptoms (cognitive impairment, neuropsychiatric symptoms, sleep disorders, autonomic dysfunction, etc.) and, as most neurodegenerative diseases, has a gradually progressive course. ¹ PD affects everyday functionality of the patients and leads at some point to disability and loss of autonomy. Among the scales measuring severity of PD, Hoehn and Yahr scale is the most widely used, semiquantifying PD severity and progression. ^{2 , 3} Concerning everyday functionality and activities of daily living (ADL), a plethora of instruments have been proposed, with Movement Disorder Society‐Unified Parkinson's Disease Rating Scale (MDS‐UPDRS) (both full scale and part II) and Schwab and England ADL scale being the preferred tools in the literature and in everyday clinical practice. ⁴ Beyond a certain stage of the disease, driving fitness is impaired among PD patients, as safe driving requires both motor/somatosensory skills and cognition to be intact. ⁵ A relative meta‐analysis has shown that PD patients (mean disease duration: 6.7 years) will more likely fail an on‐road driving test and have a more than twofold crash risk in driving simulator tests than their healthy counterparts. ⁶ It is also evident in the literature that PD patients have a gradual deterioration of their driving ability ⁷ and cease driving earlier than controls. ⁸ However, driving cessation not only reduces even more the independence of the patients, making transportation extremely difficult, but also has a detrimental effect on their self‐esteem, contributing decisively to psychosocial isolation. ⁹ The effect of PD on driving ability is complex and multilevel and originates from two main sources: (1) the wide spectrum of PD symptomatology: motor or motor control impairment, cognitive impairment (executive and visuospatial functions are vital for safe driving and may be impaired early in the disease course ^{10 , 11} ), neuropsychiatric symptomatology (depression, apathy, irritability, psychotic symptoms), daily fluctuations (wearing‐off phenomenon has a negative impact on driving and due to its fluctuating nature may be missed in a typical office‐based assessment), and sleep disturbances (daytime sleepiness and insomnia) all may have a detrimental effect on safe driving ¹² ; and (2) drugs' adverse effects that intermingle with the aforementioned symptomatology and may further deteriorate driving fitness ¹³ (eg, excessive daytime sleepiness or sleep attacks caused by dopamine agonists, ¹⁴ behavioral disturbances caused by both dopamine agonists and levodopa [l‐dopa], and dyskinesias caused by both dopamine agonists and l‐dopa that tend to fluctuate during the day, making their diagnosis and treatment challenging).

PD patients will at some point of their disease course face driving difficulties or will have to cease driving. Treating neurologists are frequently asked to evaluate driving fitness of their patients and provide evidence‐based consultation. Thus, two questions arise. First, based on what evidence (from motor and cognitive evaluation) will the doctor in charge advise these patients about their driving fitness? Second, could any professional other than the neurologist successfully assess the driving fitness of a patient with PD? The aim of the current study is to answer these two questions through the critical review of the existing national or international guidelines regarding driving fitness of patients with PD. We consider this information useful—if not necessary—not only for neurologists, given the chronic progressive course of PD and the consequent unique therapeutic relationship between physicians and patients.

Patients and Methods

We designed and performed our systematic review adhering to the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines, following the PRISMA checklist and the PRISMA flow diagram. Our search was a three‐step procedure: we initially applied our search to the U.S. National Library of Medicine database (MEDLINE via PubMed) using terms to identify PD (“Parkinson's disease” or “parkinsonism” or “extrapyramidal”) along with terms referring to driving (“driving” or “automobile driving” or “motor vehicles” or “road safety”) and guidelines (“guidelines” or “consensus” or “statement” or “recommendation”). During the second step, we expanded our search to Google Scholar, to include guidelines possibly not published as scientific papers and thus not indexed in MEDLINE (eg, national guidelines from transportation authorities). The third (final) step consisted of a search through the reference lists of the selected articles to identify articles meeting the inclusion criteria. We must note that we followed a similar search strategy to our previous report regarding the driving guidelines for patients with cognitive impairment. ¹⁵

Inclusion criteria were the following:

1. Articles should be consensus statements, recommendation papers, official guidelines, articles reviewing the abovementioned guidelines, or position papers, published by:

   1. A national committee or authority (eg, New Zealand Transport Agency).
   2. An international working group or a scientific society (eg, American Academy of Neurology).
   3. An expert or several experts on the subject “Driving and Parkinson's Disease.”

2. Articles should refer to patients with Parkinson's disease. Articles referring exclusively to PD dementia without taking into consideration any other cardinal feature of PD were excluded. Any other cause of parkinsonism (drug‐induced, vascular, atypical parkinsonian syndromes) was excluded from further analysis.

3. Articles should refer solely to active drivers of private vehicles. Commercial vehicle drivers were excluded.

For articles with more than one edition published, the most recent edition was included. We excluded articles published before 2009 and articles with no full text in English. Last literature update was made in December 2022. The flow diagram of our review is shown in Figure 1 and is based on PRISMA directives, as mentioned earlier.

FIG 1.

The flow diagram of the systematic review, based on PRISMA directives. PRISMA, Preferred Reporting Items for Systematic Reviews and Meta‐Analyses.

After our initial search in MEDLINE, we found 109 articles, and after screening the titles and abstracts, 85 were excluded as they referred to irrelevant topics. We obtained full texts of the remaining 24 articles, and we excluded 14 as they did not meet the inclusion criteria. We thoroughly assessed the 10 remaining articles, along with 15 additional articles retrieved either from Google Scholar (4 articles) or through the references list search (11 articles). Ten articles were excluded from further analysis for various reasons; finally, 15 articles were included in our review.

We critically reviewed these 15 articles to identify the following elements ¹ : general characteristics of each publication (type of study: national guidelines/recommendation paper/expert opinion, date of publication, authors and country of origin), ² proposed procedure and evaluators of driving fitness of PD patients, ³ and specific tests and scales (or red‐flag signs) used in the evaluation to assess the effect of PD on driving fitness (motor and visual assessment, neuropsychological tests, scales of overall PD burden).

Based on the findings of our review, we present a graphic representation of driving fitness evaluation procedure, along with a list of red flags derived from our review findings (Fig. 2). The red flags included were subsequently characterized based on the level of the underlying evidence.

FIG 2.

Graphic representation of the proposed procedure for driving fitness evaluation of PD patients along with a list of red flags for unsafe driving (in parentheses the level of underlying evidence). ADL, activities of daily living; AEs, adverse events; AVLT, Auditory Verbal Learning Test; CDR, clinical dementia rating; CDT, Clock Drawing Test; HVLT, Hopkins Verbal Learning Test; H&Y, Hoehn and Yahr scale; MDS, Movement Disorders Society; MMSE, Mini‐Mental State Examination; MOCA, Montreal Cognitive Assessment; PD, Parkinson's disease; ROCF, Rey Osterrieth Complex Figure Test; TMT, Trail Making Test; UFOV, Useful Field of View Test; UPDRS, Unified Parkinson's Disease Rating Scale.

Results

We identified 15 articles meeting our inclusion criteria (Table 1): nine national guidelines (60%), five recommendation papers ^{16 , 17 , 18 , 19 , 20} (33%), and one consensus statement ²¹ (7%). The national guidelines originated from seven countries:

1. Australia ²² (Austroads and National Transport Commission, endorsed by Australian and New Zealand Association of Neurologists‐2017)

2. Canada (the first paper from the Canadian Medical Association‐2012 ²³ and the second paper from the Canadian Council of Motor Transport Administrators‐2021 ²⁴ )

3. Ireland ²⁵ (National Office for Traffic Medicine, Royal College of Physicians of Ireland and Road Safety Authority‐2017)

4. New Zealand ²⁶ (New Zealand Transport Agency‐2014)

5. Singapore ²⁷ (Singapore Medical Association‐2011)

6. United Kingdom ²⁸ (Driver and Vehicle Licensing Agency with advice from the Honorary Medical Advisory Panels‐2018)

7. United States (the first paper from the National Highway Traffic Safety Administration and the American Association of Motor Vehicle Administrators‐2009 ²⁹ and the second paper from the American Medical Association‐2010 ³⁰ )

TABLE 1.

Basic characteristics of the included articles

Ref	Year	Type	Country (author)	Initial evaluator	Second‐line evaluator	Suggested follow‐up	Suggested conditional licenses
1 22	2017	National guidelines	Australia	Treating doctor (NSF)	Driver licensing authority Practical driving assessment	12 m	Yes (MOTOR = vehicle adaptations, COGNITIVE = driving during off‐peak only; drive within a 20‐km radius of place of residence; in daylight hours only; no freeway driving)
2 23	2012	National guidelines	Canada (CMA)	Treating doctor (NSF)	Driver licensing authority Practical driving assessment	Periodic, not further defined. Early stages fit to drive	YES (MOTOR = vehicle adaptations)
3 24	2020	National guidelines	Canada (CCMTA)	Treating doctor (NSF)	Driver licensing authority Practical driving assessment	5 yr	Yes (MOTOR = vehicle adaptations, VISUAL = vehicle adaptations)
4 25	2017	National guidelines	Ireland (RCPI‐RSA)	GP	Multidisciplinary evaluation by specialists Practical driving assessment	Regular reevaluation	Yes (MOTOR = vehicle adaptations, COGNITIVE = avoid demanding situations: only daytime diving, driving in a restricted radius, speed restriction)
5 16	2012	Recommendation paper	AAN (Crizzle et al.)	Neurologist	Multidisciplinary evaluation (neurologist, neuropsychologist, CDRS) Driver licensing authority Practical driving assessment	–	No
6 17	2016	Recommendation paper	Jitkritsadakul and Bhidayasiri	Treating physician (GP/neurologist)	Driver licensing authority Practical driving assessment	Annual	No
7 18	2020	Recommendation paper	Falkenstein et al.	GP	Specialist	Regular reevaluation	Yes (MOTOR = vehicle adaptations, COGNITIVE = avoid demanding situations)
8 26	2014	National guidelines	New Zealand	GP	OT Practical driving assessment Specialist	Annual	Yes (annual review)

9 21	2014	Consensus statement	Classen	OT	Practical driving assessment	Annual	Yes (MOTOR = vehicle adaptations, COGNITIVE = driving restrictions, not specified)
10 28	2018	National guidelines	UK	GP	Driver licensing authority	Regular review	Yes (MOTOR = vehicle adaptation)
11 27	2011	National guidelines	Singapore	GP	Specialist Practical driving assessment	–	No
12 29	2009	National guidelines (NHTSA and AAMVA)	USA	Treating physician (NFS)	OT, CDRS Practical driving assessment	Periodical reevaluation	Yes (MOTOR = vehicle adaptations)
13 30	2010	National guidelines (AMA)	USA	Treating physician (NSF)	CDRS Practical driving assessment Specialist	6–12 mo	Yes (MOTOR = vehicle adaptations, COGNITIVE = driving restrictions‐geographic areas/conditions)
14 19	2021	Recommendation paper	Charmley et al.	Treating team (neurologist, neurosurgeon)	–	–	Yes (6‐week driving restriction)
15 20	2013	Recommendation paper (battery)	Devos et al.	Treating physician (NSF)	Practical driving assessment CDRS	–	–

Abbreviations: NSF, no specialty defined; CMA, Canadian Medical Association; CCMTA, Canadian Council of Motor Transport Administrators; RCPI‐RSA, Royal College of Physicians of Ireland‐Road Safety Authority; GP, general practitioner; AAN, American Academy of Neurology; CDRS, certified driving rehabilitation specialist; OT, occupational therapist; NHTSA, National Highway Traffic Safety Administration; AAMVA, American Association of Motor Vehicle Administrators; AMA, American Medical Association.

All articles referred to active drivers of private vehicles suffering from PD, whereas in one article recommendations were made exclusively for PD drivers after deep brain stimulation surgery. ¹⁹

The first issue we aimed to address through the present review is the composition of driving fitness evaluation of PD patients. Our findings suggest that the evaluation should consist of the following six aspects: (1) general characteristics of the patient, proposed in 5 of 15 articles (33%), for example, disease duration and severity measured using Hoehn and Yahr scale, patient's age, and comorbidities; (2) driving history, including history of accidents or near accidents, recommended in only 3 of 15 articles (20%); (3) motor impairment, identified in the neurological examination and usually quantified using MDS‐UPDRS‐III, recommended in all 15 articles (100%); (4) cognitive assessment, proposed in 13 of 15 articles (87%); (5) visual assessment, proposed in 8 of 15 articles (53%); and (6) significant PD features: sleep disorders (5 of 15 articles, 33%), motor fluctuations (6 of 15 articles, 40%), neuropsychiatric symptomatology (2 of 15 articles, 13%), and drugs' adverse effects (9 of 15 articles, 60%).

Despite the unanimously recognized need for motor assessment, specific methodology or tests are proposed in only 8 of 15 articles (53%), whereas relative cutoff values are indicated in only 50% of them (4 of 15, 26%). The most encountered motor test is the Rapid Paced Walk (RPW) Test (five articles), followed by the manual tests of motor strength and range of motion (in four and three articles, respectively) and the MDS‐UPDRS‐III (proposed in four articles).

Concerning cognitive assessment, specific neuropsychological tests or scales and their cutoff values are proposed in 7 and 4 of 15 articles, respectively; use of Trail Making Test‐B (TMT‐B) is supported in five articles and Clock Drawing Test and Mini‐Mental State Examination in three articles each. Examination of vision and relative cutoff values is included in 7 and 3 of 15 articles, respectively. According to these articles, a driver with PD should undergo testing for visual acuity (proposed in four articles), visual fields (either by visual confrontation or by the Useful Field of View test, each proposed in three articles), and contrast sensitivity (4 of 15 articles).

The aforementioned along with the relative references 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88 are analyzed further in Table S1 (available in Supplementary Material).

Moving forward to our second basic research question (“could any professional, other than the neurologist, assess driving fitness of PD patients?”), a common pattern encountered in eight articles (53%) is the initial evaluation from the treating physician. The treating physician could be a general practitioner (GP), proposed in 6 of 15 articles, or a neurologist, proposed in only 2 of 15 articles, whereas in one article an occupational therapist is proposed as the initial evaluator. In six articles the specialty of the initial evaluator is not specified although we can suppose that, when it comes to PD patients, treating physicians are mainly neurologists. If the patient is found fit to drive, the treating physician should perform periodic reevaluations of driving fitness (as proposed in 11 articles [73%]), given the gradually progressive, neurodegenerative nature of PD. Proposed reassessment period ranges from 6 months to 5 years, but it is worth noting that in most of the included articles (7 of 11) the reassessment period is not defined.

In undetermined cases, the initial evaluator should refer patients for a second‐line evaluation (SLE), proposed in 14 articles (93%). SLE may include a practical driving assessment (proposed in 12 articles, 80%), assessment from a multidisciplinary team (proposed in 2 articles, 13%), medical assessment from a PD specialist (proposed in 4 articles, 26%), or assessment from a driving rehabilitation specialist (proposed in 4 articles, 26%). In such cases, the final decision about driving fitness still lies on the treating physician, who must incorporate the results of SLE in his or her initial evaluation. Alternatively, the treating physician can refer PD patients to driver licensing authority (six articles, 40%) to make a final decision regarding driving fitness. Conditional licenses are proposed in 11 of 15 articles (73%) to facilitate driving for PD patients and thus to reduce the risk of unexpected events. Restrictions may be either vehicle adaptations proposed in nine articles, ^{18 , 21 , 22 , 23 , 24 , 25 , 28 , 29 , 30} which simplify the operational level of driving (eg, special controls, automatic transmission), or avoidance of specific high‐risk conditions, proposed in six articles ^{18 , 19 , 21 , 22 , 25 , 30} (eg, driving only during daylight hours or in a restricted radius). For further information refer to Table 1.

Conclusion

Driving fitness of PD patients is an expanding field of research, given the neurodegenerative nature of PD and its multidimensional effect on the nervous system and consequently on driving ability. Previous reviews ^{6 , 10 , 17 , 89 , 90 , 91 , 92} have circumscribed the research data, which mainly come from on‐road studies or driving simulator experiments. The aim of the current study was to go beyond this approach; we performed a systematic review of the literature to identify guidelines/recommendations (GRs) worldwide regarding driving fitness of PD patients. We consider these directives to be irreplaceable for the treating neurologist in everyday clinical practice as they could navigate him or her in the evaluation procedure and thus in decision‐making and consultation.

We identified 15 GRs, a relatively small number, given the prevalence of PD, its potential effect on driving fitness, and the plethora of research studies on the subject “PD and driving.” This discrepancy may arise from one main and many secondary methodological research problems. The main problem is the lack of a gold‐standard method to evaluate driving fitness of PD patients, which would allow the estimation of sensitivity and specificity of any other method and the production of concrete guidelines. On‐road tests are generally used as the gold‐standard method to evaluate driving fitness, given their ecological validity and their efficiency to evaluate the three main levels of safe driving: strategic, operational, and tactical. ⁹³ However, the plethora of on‐road tests proposed in the literature, along with their important methodological differences and the lack of large‐scale studies, narrow the generalization of results. ⁹⁴ A systematic review of standardized on‐road tests among people with cognitive impairment had mixed results with limited value in clinical decision‐making. ⁹⁵ To our knowledge, there is no such study for PD patients in the literature. Other methodological obstacles include scarcity of data on real‐life driving behavior of PD patients and difficulty to incorporate research tools (eg, driving simulator or equipped vehicles for naturalistic driving) in everyday practice due to high cost and limited availability.

As mentioned earlier, proposed methods or batteries to evaluate driving fitness are usually compared to performance in an on‐road test. These studies show that physicians (based on clinical evaluation) may overestimate PD patients' driving proficiency, ^{16 , 96 , 97} whereas clinical screening batteries suggest several cognitive, motor, and visual parameters as possible predictors of on‐road driving performance. ^{16 , 98} However, these results are inconsistent or have only moderate prognostic value when compared to on‐road tests. ^{16 , 99 , 100 , 101 , 102} Adding driving simulator data to a screening battery may improve prognostic value. ¹⁰¹ It is to be noted that (as a naturalistic study has shown) PD patients seem to acknowledge their difficulties, restricting their driving practices and avoiding demanding driving situations. ⁸⁹

Among the 15 articles included in our review, only nine are official national guidelines, from seven countries (Canada and the United States have published two different guidelines each, from different authorities). The need of evaluating both mobility and cognition of drivers with PD is established in almost 90% (13 of 15) of GRs. However, there are inconsistent directives regarding the most appropriate motor or cognitive tests. Except for TMT‐B and RPW (each proposed in five articles), another 14 motor and 18 cognitive tests are recommended in the GRs. Table S1 shows that these tests are commonly based on arbitrary or heterogeneous data and, most important, cutoff values are lacking. Other key features of PD that may affect driving fitness (visual impairment, neuropsychiatric symptoms, daily fluctuations, sleep disorders, antiparkinsonian drugs' adverse effects, and data from clinical and driving history) are underrepresented in GRs.

The concepts of trichotomization in safe drivers, unsafe drivers, and undetermined cases, (already described in our previous report on driving and dementia ¹⁵ ) along with a two‐leveled evaluation (in undetermined cases) and the need of periodical reevaluation of driving fitness are reproduced in the majority of the GRs. However, the proposed reassessment period varies from 6 months to 5 years or is not even defined. An important issue that is also not addressed in the guidelines is the possibility of reevaluation of the “unsafe” drivers after a certain period of driving rehabilitation. Three simulator studies have shown positive results, ^{103 , 104 , 105} but due to their small samples and their experimental nature, they are not incorporated in the GRs of our review and, for the time being, have a restricted clinical significance. However, driving rehabilitation is a promising field of research, given the negative psychosocial impact of driving cessation. ⁹

In most articles the key role of the treating physician is recognized, as he or she is responsible for the initial evaluation, the periodic reevaluations (of “safe” drivers), and the referral to SLE in undetermined cases. The treating physician is proposed to be either a GP or a neurologist. In our point of view, the treating neurologist is the most appropriate initial evaluator, as he or she not only “knows the disease” (being a neurologist) but also “knows the patient” (being the treating physician). Thus, neurologists can objectively assess all the key components of safe driving (including motor and cognitive assessment) and incorporate them in the initial evaluation of driving fitness. Also, they can perform reevaluations in the frame of regular follow‐up visits, ensuring the early detection of deterioration.

The promising patterns described earlier (trichotomization, two‐leveled evaluation, unique role of treating physician, periodical reevaluations) are not further formulated in the GRs in a clear, concrete procedure to assess driving fitness. Figure 2 schematically shows the procedure to evaluate driving fitness of PD patients, proposed in the majority of the GRs. We have added a list of red flags derived from our review findings. These red flags are categorized into the six main aspects of driving fitness evaluation analyzed in our “Results” section (1. data from the clinical history, 2. data from driving history [after interview with the patient and the caregiver], 3. motor function evaluation, 4. cognitive assessment, 5. examination of vision, and 6. special PD features) and are also characterized according to the level of the underlying evidence based on the American Academy of Neurology Classification of evidence. ¹⁰⁶

Except for the methodological problems discussed earlier, our study has a few limitations. We included only English‐language articles and, thus, we may have missed GRs written in other languages. Furthermore, our search strategy (described in Patients and Methods) possibly would not detect any GRs published from nonscientific sources (eg, governmental documents) or not published online.

Future large‐scale studies are needed to reach a consensus regarding the ideal evaluation procedure of driving fitness among PD patients. Emphasis should be given to the establishment of certain motor, cognitive, and visual tests as risk factors of unsafe driving, along with relative cutoff values. Such a goal requires both observational (cross‐sectional and longitudinal) studies regarding real‐life driving behavior of PD patients and correlational studies to identify possible predictors of driving fitness. One critical issue is the generalizability of the results, which is feasible only through the careful selection of the study population, the implementation of a common widely accepted evaluation procedure (regarding office‐based tests and practical driving assessments), and the constitution of international, multidisciplinary working teams. Driving rehabilitation of PD patients is also a promising research field with the potential of a game changer in driving fitness evaluation.

Author Roles

(1) Research project: A. Conception, B. Organization, C. Execution; (2) Statistical analysis: A. Design, B. Execution, C. Review and critique; (3) Manuscript: A. Writing of the first draft, B. Review and critique.

P.S.: 1A, 1B, 1C, 2A, 2B, 2C, 3A, 3B

A.E.: 1A, 1B, 2C, 3B

G.Y.: 1A, 1B, 2C, 3B

L.S.: 1A, 1B, 2C, 3B

S.G.P.: 1A, 1B, 1C, 2A, 2C, 3B

All authors have read and approved the final manuscript.

Disclosures

Ethical Compliance Statement: The authors confirm that neither the approval of an institutional review board nor patient‐informed consent was required for this work. We confirm that we have read the journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines.

Funding Sources and Conflicts of Interest: Petros Stamatelos received a scholarship for his PhD project titled “Evaluation of Driving Behavior of Patients with MCI, Dementia or Parkinson's Disease: Diagnostic and Prognostic Markers,” by Alexander S. Onassis Public Benefit Foundation (grant number: G ZN 060‐1/2017‐2018).

Financial Disclosures for the Previous 12 Months: Petros Stamatelos and Alexandra Economou have nothing to declare. George Yannis received funding from the European Commission—DG Move/European Commission—DG RTD/Hellenic Ministry of Infrastructure and Transport/Hellenic Ministry for Development/Cyprus Ministry of Transports/Organisation for Economic Cooperation and Development/World Road Association—PIARC/World Bank (nothing related to the current manuscript). Leonidas Stefanis received funding from PPMI2 (supported by The Michael J. Fox Foundation), IMPRIND‐IMI2 number 116060 (EU, H2020), “Transferring Autonomous and Non‐autonomous Cell Degeneration 3D Models between EU and USA for Development of Effective Therapies for Neurodegenerative Diseases (ND)—CROSS NEUROD” (H2020‐EU 1.3.3, grant number 778003), “Chaperone‐Mediated Autophagy in Neurodegeneration” (Hellenic Foundation for Research and Innovation Grant HFRI‐FM17‐3013), “ALAMEDA” (H2020‐EU, grant agreement 101017558), “Next‐Generation Antisense Molecules for Parkinson's Disease Therapy (THERASYN)” (Greek Secretariat of Research and Technology [GSRT], Collaborator), “National Network for Neurodegenerative Diseases (ΕΔΙΑΝ)” (GSRT), and “CMA as a Means to Counteract alpha‐Synuclein Pathology in Non‐Human Primates” (by The Michael J. Fox Foundation [Collaborator]). He has served on the advisory boards of AbbVie, ITF Hellas, and Biogen, and has received honoraria from AbbVie and Sanofi (nothing related to the current manuscript). Sokratis G. Papageorgiou has nothing to declare.

Supporting information

Data S1. Supporting information.