1 in 5 MS Patients May Be Unfit to Drive, But More Research Is Needed

About one in five people with multiple sclerosis (MS) may be unfit to drive a vehicle due to disease-related difficulties, according to a review of published studies.

Cognitive and visual difficulties were most frequently associated with impaired driving ability, both on the road and in a simulation. However, the pooled evidence was inconsistent for most studied outcomes, with some studies reporting conflicting results.

“Further high-quality research in driving in PwMS [people with MS] is needed to enable us to make more accurate predictions of fitness to drive, and to keep PwMS and other road users safe,” researchers wrote.

The study, “Driving ability and predictors for driving performance in Multiple Sclerosis: A systematic review,” was published in the journal Frontiers in Neurology.

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Driving ability can be impaired by MS symptoms

Driving is important for many people living with MS to help them navigate their daily tasks and work, social, and health-related affairs. However, driving ability can be impaired by several disease symptoms, including visual problems, mobility issues, and cognitive impairment.

Evidence suggests that people with MS commit more driving violations and are more frequently involved in car accidents. Yet, there are no clear guidelines to assess the driving fitness of MS patients, and only two tests seem to accurately predict their driving ability.

This leads to many decisions being made about a patient’s driving ability, at both the clinic and government levels, without evidence-based resources.

“Therefore, there is an urgent need not only for clinicians but also for lawgivers and traffic authority personnel to have fair and reliable regulations and guidelines to evaluate driving abilities in PwMS,” the researchers wrote.

With this in mind, a team of researchers in Europe conducted a systematic review of studies, published up to Jan. 1, 2022, that assessed driving performance in people diagnosed with MS. They focused only on studies that investigated driving outcomes in either on-road driving or in a driving simulator with a steering wheel, and brake and accelerator pedals.

Further high-quality research in driving in PwMS [people with MS] is needed to enable us to make more accurate predictions of fitness to drive, and to keep PwMS and other road users safe

Researchers set out to test the effect of MS on driving ability

The goal was to evaluate the effect of MS on driving and to identify possible predictors of driving ability.

Of an initial 4,081 studies, 24 were included in the review: 14 featuring on-road tests and 10 that used a driving simulator. Overall, the 24 studies included 806 people with MS and 280 people without the disease who served as controls. Most studies (19) were done in the U.S. and Canada; the remaining five were conducted in Europe.

The researchers noted that the large variety in outcome measures, study designs, and characteristics of the included patients precluded a meta-analysis, which is an analysis that pools data from multiple studies to more confidently assess a given association.

Among the on-road driving studies, the proportion of patients failing to pass a driving test ranged from 6%–38%, with the proportion in most studies falling between 17% and 23%. Poor responses to important road information and miscalculations in assessing gaps between cars were the issues most frequently found in participants who failed the test. Lack of lane maintenance and speed regulation were also predictors of a failed road test.

Likewise, assessments done in a simulator also revealed several issues. Compared with controls, people with MS had more difficulties in several aspects of driving, including speed regulation, road tracking, concentration, and response to changes.

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Cognitive, visual impairments consistently linked to reduced driving ability

Next, the researchers assessed the pooled evidence for possible predictors of driving ability. Difficulties in cognitive tests and visual impairments, particularly in processing speed and visual acuity, were found to be the most consistently associated with reduced driving performance.

By contrast, very little or no associations were found between driving ability and fatigue, MS-related factors such as disease course and duration, and disability, or age. These last two might be linked to an overall study population that was relatively young (mean ages ranging from 36 to 55 years), with only low to moderate disability.

However, “most of the evidence presented in this review showed heterogeneous results,” the research team wrote, highlighting the inconsistencies and contradictions found between studies. These included inconclusive assessments on the effect of depression and anxiety, and of several subdomains of cognition, including executive function, learning and memory, and attention and information processing.

These findings show that the current level of evidence is insufficient to properly develop guidelines for assessing driving ability in people with MS, emphasizing the need for more research on the topic.