Drivers with Parkinson's disease: who participates in research studies?

Concern about the effects of Parkinson's disease (PD) on driving competence has precipitated many studies, although most have consisted of small samples. Findings are difficult to interpret and compare as researchers have employed different inclusion/exclusion criteria and rarely provide information on the number of PD patients who are no longer driving, fail to meet other criteria, or refuse to participate.

The present study examined barriers to participation and representativeness of research participants by screening PD patients at a movement disorder research center to develop a profile of patients who were currently driving versus those who had stopped driving, and to ascertain eligibility and willingness to participate in driving research.

Over 13 months, 128 PD patients were screened (mean age 69.2 ± 10.1; range 39-90); 62% men; with UPDRS motor scores ranging from 8.5 to 68 (mean 30.3 ± 11.3). Only 66% were still driving, and compared to those who had stopped driving, current drivers were more likely to be men (p < .05), younger (p < .05), experienced less severe motor dysfunction (p < .001) and were less likely to report freezing symptoms (p < .05). Less than half (48%) who were eligible for the study agreed to participate. The primary reasons for refusal was having their driving assessed and fear of being reported to licensing authorities.

Recruitment of women and participants from various ethnic, educational and socioeconomic backgrounds are important when considering the generalizability of study findings and are needed to develop fitness to drive guidelines in persons with PD.