Historically, research regarding diabetes mellitus (DM) and driving automobiles centered around medical emergencies often related to hypoglycaemic events (American Diabetes Association, 2012). Understanding the impediments from DM peripheral neuropathy and relating that to driving automobiles is a recent area of focus. It is important that podiatrists, as well as other healthcare professionals, recognise the potential limitations from DM and discuss these concerns with patients to improve safety of all road users.
Diabetes is a significant concern in the US, impacting approximately 13% of the population older than 18 years (National Diabetes Statistics Report, 2020). Estimates suggest that 60–70% of people with DM will develop mild to severe peripheral neuropathy with affects to the sensory, motor, and autonomic nerves (National Institute of Neurological Disorders, 2020).
Peripheral sensory neuropathy may result in the loss of protective sensation, temperature discrimination, and proprioception. This limits biofeedback for a person interacting with their environment (Pop-Busui et al, 2017). This loss of sensation could be further complicated by motor neuropathy or decreased muscle innervation, as a late finding. The mechanism of motor neuropathy is still not fully understood. However, there is evidence that people with type 2 DM have decreased strength in the lower extremities with an increased quantity of intramuscular noncontractile tissue (Almurdhi et al, 2016).
Using driving simulators, participants with DM and related peripheral neuropathy demonstrated delayed braking response time (Spiess and Meyr, 2017; Spiess et al 2017), altered speed of strength generation and increased ankle reposition error (Perazzolo et al, 2019). These studies suggest that DM-associated peripheral neuropathy could have an adverse effect on a person’s driving ability. To understand healthcare providers’ impact on the patient’s own acknowledgement of their driving limitations, the authors chose to survey US podiatrists. The aim was to determine if driving automobiles was a topic podiatrists discussed with patients that have DM lower-extremity complications.
Methods
The authors created a questionnaire on a popular online survey platform (Qualtrics®XM, Provo, Utah). The aim was to survey podiatrists across the US. Given this undertaking, since nationwide totals between 10,500 jobs (US Bureau of Labor Statistics, 2021) and up to 18,000 licensed podiatrists (American Podiatric Medical Association, 2021), the authors reached out to national and state associations for support in distributing the survey. It was then shared through member-only newsletters and websites. Additional dissemination ensued through internet email mining by the authors. The survey recruitment lasted for approximately 5 months, between November 2018 and March 2019.
The survey determined if podiatrists discussed driving automobiles with patients that have lower-extremity complications associated with DM. The respondents could proceed if they answered yes.
When a ‘yes’ was selected, respondents were given a list of examples to select what prompts the discussion and further breakdown the reasoning. Finally, they were asked if they offered recommendations to the patient on changing driving activity.
Results
A total of 541 podiatrists volunteered and responded to the survey, with 497 completed responses. Of the 50 states, providers from 41 states responded to the survey. The states with the highest responder rates were Illinois, New Jersey and New York. Missing states were Alaska, Hawaii, Louisiana, Maryland, Mississippi, Nevada, Rhode Island, South Dakota and Wyoming. Podiatrists were from city, urban, and rural locations, in private, multi-specialty, and institutional practice settings.
The initial results were split, as 51% reported that they did engage in driving discussions with the patient and 49% did not. Of the podiatrists that discussed driving with patients, explanations were offered to understand what prompted the conversation. From this selection, the most common reason a driving discussion occurred was the presence of DM with peripheral neuropathy (Table 1), with the specific physical exam finding of loss of sensation distal to the ankle (Table 2). Following this was the presence of a diabetic foot ulcer (DFU). Other common prompts included post-op surgical course, gait instability or abnormality, and use of an offloading device.
Most podiatrists (90%) reported they advised to change driving activity. Options for the patients include temporary or permanent driving restrictions, limiting driving for necessary trips only, and offering information for alternative modes of transportation (Table 3).
Discussion
Diabetes prevalence continues to rise in the US. The most recent reports suggest approximately 10.5% of the US population have DM, with additional estimates that DM is found within 13% of the US population aged 18 years or older (National Diabetes Statistics Report, 2020). Diabetes continues to be the leading cause for polyneuropathy in the US (National Institute of Neurological Disorders, 2020). Between 60–70% of people with DM will develop mild to severe peripheral neuropathy, leading to deficits in sensory, motor and autonomic nerves (National Institute of Neurological Disorders, 2020).
The literature on how DM peripheral neuropathy affects driving automobiles is limited. Multiple reports have demonstrated the benefits and validity of using driving simulators to measure brake response times, lateral positions, inattention, etc. (Blana, 1996; Hoskins and El-Gindy, 2006; Casutt et al, 2013; Sahami and Sayed, 2013; Meuleners and Fraser, 2015). Driving simulators have suggested participants with DM and related peripheral neuropathy may have altered responses to the vehicle foot pedals. One study demonstrated delayed braking response time (Spiess and Meyr, 2017; Spiess et al, 2017). Another study showed altered lower-extremity speed of strength generation and increased ankle reposition error (Perazzolo et al, 2019). These investigations question the safety for the driver, and all users of the road.
According to the results of our survey, approximately 51% of US podiatrists engage in driving discussions with patients that have DM lower-extremity complications. Diabetic peripheral neuropathy is the primary prompt for this discussion, with specific focus on loss of sensation distal to the ankle. A person with DM and associated peripheral neuropathy may not be aware with how their body is directly interacting with the vehicle. Healthcare providers serve on the frontline of DM care and DM patient education. Multiple organisations focused on DM, such as the American Diabetes Association (ADA) (2021) and International Working Group on the Diabetic Foot (IWGDF) (2019), recommend that people with DM have an annual foot exam.
The ADA Standards of Medical Care in Diabetes (2021) include guidelines for frequency of DM foot exams to assess for lower-extremity complications. It recommends that all people with DM be assessed for diabetic peripheral neuropathy upon diagnosis of type 2 DM and annually after, and then 5 years after the diagnosis of type 1 DM and annually after. This annual foot exam serves as an opportune time to engage in the driving discussion with the patient and further educate patients on driving safety
When drivers were surveyed, on a scale of one to ten, people rated their own driving skills as a seven, suggesting people think their own driving is superior to what other people would determine (Roy and Liersch, 2014). The US National Highway Traffic Safety Administration recognizes that diabetes can lead to nerve damage, making sensation difficult, and that pressing the brake pedal fast enough to avoid a crash may be unfeasible. However, the US Federal Highway Administration (2014) acknowledges that a driver’s license symbolises independence and freedom. With no national driving recommendations from these organisations, it is difficult for the health care provider to intervene. Future studies should be employed to better understand the implications of DM peripheral neuropathy and driving automobiles and patient perception, to help create evidence-based guidelines.
A driving simulator may not directly parallel real life vehicle ergonomics. Human body posture and foot position is specific to the driver. In a fixed environment, a driver must adjust seat position depending on height or shoe size in relation to the seat, wheel, foot pedals, among others (Sahil and Shashank, 2017; Xi, 2018). Furthermore, vehicle ergonomic studies show that with a taller stature or larger shoe size, a foot transfers from the accelerator or brake pedal through pivoting off the heel, while with a shorter stature or shoe, the driver is more likely to transfer pedals with lifting their leg (Crandall et al, 1996; Xi, 2018). Thus, foot pedal patterns are not necessarily habitual behavior, but rather anthropometrically dependent (Xi, 2018). Future studies should focus on these ergonomic details to improve authenticity.
The survey results have limitations. The study was designed as a pilot to review if podiatrists discussed this topic with patients. The authors present the data to disseminate the activities of other podiatrists and to encourage health care providers to engage in similar conversations with their patients. This survey does not include other nations or specialties, such as primary care, endocrinology, neurology, etc. Management of DM is a multidisciplinary endeavor, and it may be possible that these other healthcare providers are engaging with patients regarding driving activity. Additionally, there may be other prompts that lead to this discussion.
Other limitations include the ongoing COVID-19 pandemic. With the widespan use of telehealth encounters, discussing driving activity may appear irrelevant. However, despite the decrease in number of motor vehicle accidents (MVA) in the US during the pandemic, preliminary studies show that the rate of MVA increased, as well as the fatality rates for both drivers and vulnerable road users for many cities (StreetsBlog USA, 2020). Another study from National Farmers Union Mutual Insurance in the United Kingdom reported that as the pandemic lockdowns ease one of four drivers were “feeling nervous” about driving for long journeys (Motoring Research, 2021). Which suggests that driving may not be as routine for people and they may or may not be cognisant of their inabilities.
Conclusion
Peripheral neuropathy is a common complication of DM, which may alter how a person perceives their environment. Recent literature has explored how this may negatively impact driving automobiles. In large parts of the world, driving automobiles is still a necessary means of life. Furthermore, outside of extremes, there is no defined logic with how and when to revoke a driver’s license, or who is responsible to do so. Future studies could focus on how people with DM and peripheral neuropathy perceive these sensory and motor deficits and if or how these affect their driving, as they are the drivers. Nonetheless, healthcare providers have an opportunity to include driving with DM peripheral neuropathy patient education and during annual DM foot exams.
