Safe Driving

One of the obligations of doctors diagnosing someone with Parkinson’s disease is to advise them to tell the DVLA (Driving and Vehicle Licensing Authority – the UK’s driving license agency) of their diagnosis. When this happens, the DVLA then sends a form to the physician to ask for a professional judgement on their risk to themselves or others on the road.

The guidance for doctors is relatively scant:

! - Must notify the DVLA. 

May drive as long as safe vehicle control is maintained at all times. 

If the individual's condition is disabling and/or there is clinically significant variability in motor function, the licence will be refused or revoked. 

If driving is not impaired, licensing will be considered subject to satisfactory medical reports. 

A licence may be issued subject to regular review.

(from https://www.gov.uk/guidance/neurological-disorders-assessing-fitness-to-drive#parkinsons-disease)

This article aims to help clinicians with some real-world evidence. They did assessments of vision, thinking and movement in healthy older adults as well as people with Parkinson’s. They then assessed their driving in a ‘kitted out’ car with lots of sensors and cameras to allow later scoring of errors etc. The participants then drove an 18 mile route in Iowa, on a mixture of road types. They then invited the participants to return two years later.

The first thing to say is that no one was told to stop the driving assessment early. The people with Parkinson’s were moderately affected (Hoehn & Yahr stage 2, where 1 is minimal symptoms affecting 1 side only – 5 being bed-bound), so the findings are not necessarily applicable to people who’ve just been diagnosed (nor those with more advanced disease).

The headlines from the paper are that people with PD made more mistakes at the beginning of the study (40 PD vs 32 controls), and two years later made significantly more mistakes (50 PD vs 35 control). Serious errors were, however, rare overall (but slightly more common in people with PD). Interestingly, when you only looked at those who did return, the baseline error rate was the same.

One large caveat that should be applied to this study is that of the 67 people with PD that started the study, only 28 returned for the 2 year assessment. 12 of these people had stopped driving in between, one had died and 26 declined the invitation to return. Significantly more healthy controls returned at 2 years (and only 1 of those that didn’t had stopped driving between assessments). Also, it should be noted that driving in Iowa is not necessarily the same as driving in the UK (indeed, driving in London is not the same as driving in Norfolk)

So how does this help me in clinic? Well, the factors that were the most significantly associated with predicting poor driving performance were – near visual acuity, change in the useful field of view, trail making tests (which measure planning and ‘executive function’) and the ability  to do everyday tasks (Activities of Daily Living on the UPDRS). Do we in the Parkinson’s field have a duty to do vision testing? It is interesting to see how different areas of research are converging – Have a look at Dr Rimona Weil’s research that has also hit the news recently 
http://www.telegraph.co.uk/science/2017/10/15/cats-dogs-helping-doctors-predict-dementia-people-parkinsons/ or directly to the research website https://vision-in-parkinsons.co.uk

RNR

http://www.neurology.org/lookup/doi/10.1212/WNL.0000000000004629

Longitudinal decline of driving safety in Parkinson disease

ABSTRACT

Objective: To longitudinally assess and predict on-road driving safety in Parkinson disease (PD).

Methods: Drivers with PD (n 5 67) and healthy controls (n 5 110) drove a standardized route in an instrumented vehicle and were invited to return 2 years later. A professional driving expert reviewed drive data and videos to score safety errors.

Results: At baseline, drivers with PD performed worse on visual, cognitive, and motor tests, and committed more road safety errors compared to controls (median PD 38.0 vs controls 30.5; p , 0.001). A smaller proportion of drivers with PD returned for repeat testing (42.8% vs 62.7%; p , 0.01). At baseline, returnees with PD made fewer errors than non-returnees with PD (median 34.5 vs 40.0; p , 0.05) and performed similar to control returnees (median 33). Baseline global cognitive performance of returnees with PD was better than that of non-returnees with PD, but worse than for control returnees (p , 0.05). After 2 years, returnees with PD showed greater cognitive decline and larger increase in error counts than control returnees (median increase PD 13.5 vs controls 3.0; p , 0.001). Driving error count increase in the returnees with PD was predicted by greater error count and worse visual acuity at baseline, and by greater interval worsening of global cognition, Unified Parkinson’s Disease Rating Scale activities of daily living score, executive functions, visual processing speed, and attention.

Conclusions: Despite drop out of the more impaired drivers within the PD cohort, returning drivers with PD, who drove like controls without PD at baseline, showed many more driving safety errors than controls after 2 years. Driving decline in PD was predicted by baseline driving performance and deterioration of cognitive, visual, and functional abnormalities on follow-up. Neurology® 2017;89:1–8