Driving with Dementia

A systematic review and meta-analysis² of risk of motor vehicle collisions (MVCs) and driving impairment related to dementia searched 7 databases for studies published in English only after 2004. This included studies with mild, moderate, or severe dementia. Analysis included 9 studies covering 378 patients with dementia and 416 healthy controls.

Just two studies over the past 10 years compared MVCs in dementia patients with healthy controls. One study showed over four times increased risk of MVCs for every 1,000 miles driven per week, over the course of three years.³ The other study showed no statistically significant increase in MVCs over the same time span.⁴ The studies relied mainly on proxy reporting and evidence on increased MVC risk with dementia is inconclusive.

Impaired Driving in Very Mild Dementia
Pooled analysis of 4 studies showed that dementia is linked to over ten times increased risk of failing a road test vs healthy controls (RR: 10.77, 95% CI: 3.00–38.62, p < 0.001).
Risk of failed road test increased even in very mild dementia:
-Very mild dementia: absolute risk increase 11% to 12%
-Mild dementia: absolute risk increase 18% to 22%
Other red flags: Problems identifying landmarks/signs, lost trips, not wearing a seatbelt, less freeway driving, more driving close to home, daylight only driving

Wide range of diagnostic criteria for MCI complicates comparisons between studies
-Results may underestimate the effect of dementia on driving impairment if studies did not carefully screen controls for MCI
-Possible selection bias: patients who feared license withdrawal or had more driving impairment may not have participated
-English only studies, few studies on moderate dementia

Earlier Intervention to Improve Driving Safety in Dementia
“Altogether, it seems that the time to raise concerns over driving safety might be earlier on in the disease process, such as when individuals have diagnoses of MCI, preclinical dementia, or even very mild dementia. At these earlier stages, drivers may be less familiar with their personal limitations and may opt to take more risks,” first author Justin Chee, MSc, University of Toronto, and colleagues

Take Home Points
-Systematic review and meta-analysis found dementia may be linked to over ten times increased risk of failing a driving test, and the risk is increased in even very mild and mild dementia
-Evidence on increased MVC risk related to dementia is inconclusive due to conflicting evidence and small number of studies
-Earlier intervention when individuals have a diagnosis of MCI, preclinical dementia, or very mild dementia may improve driving safety

References
1. Vaughan L, Hogan PE, Rapp SR, et al. Driving with Mild Cognitive Impairment or Dementia: Cognitive Test Performance and Proxy Report of Daily Life Function in Older Women. J Am Geriatr Soc. 2015;63:1774-1782.
2. Chee JN, Rapoport MJ, Molnar F, et al. Update on the Risk of Motor Vehicle Collision or Driving Impairment with Dementia: A Collaborative International Systematic Review and Meta-Analysis. Am J Geriatr Psychiatry. 2017;25:1376-1390.
3. Ott BR, Heindel WC, Papandonatos GD, et al. A longitudinal study of drivers with Alzheimer disease. Neurology. 2008;70:1171-1178.
4. Davis JD, Papandonatos GD, Miller LA, et al. Road test and naturalistic driving performance in healthy and cognitively impaired older adults: does environment matter?J Am Geriatr Soc. 2012;60:2056-2062.