What is the motor vehicle crash risk for drivers with a sleep disorder?

In many parts of the world, drivers with serious sleep disorders have restrictions on their licence – with the fitness-to-drive criteria varying across licensing jurisdictions. This study aimed to systematically review the literature that evaluated the available scientific evidence for the relationship between sleep disorders and two driving safety outcome measures: (i) motor vehicle crashes (MVC) and (ii) on-road driving test outcome. This review was registered with PROSPERO in July 2019 (see CRD42019144643). A systematic search of public health, psychology and transport databases was conducted on November 8th, 2019. The quality of evidence for each study was rated using the National Heart, Lung and Blood Institute Quality Assessment tools. Thirty-nine studies published between 1976 and 2015 met the inclusion criteria (n = 9 case-control; n = 24 cohort/cross-sectional; n = 6 before-after). Overall, the quality of evidence for 22 studies was rated as ‘good’, nine as ‘fair’ and eight as ‘poor’. Included studies addressed: sleep apnoea and sleep-related breathing disorders (n = 35); central disorders of hypersomnolence and narcolepsy (n = 5), and insomnia (n = 2), with some studies covering multiple sleep disorders. Of the thirty-five studies specifically investigating MVC risk associated with sleep apnoea, eighteen studies reported an increased risk (n = 11 ‘good’, n = 4 ‘fair’, n = 3 ‘poor’ quality), seven reported no difference in risk (n = 3 ‘good’, n = 4 ‘fair’ quality), and two provided inconclusive findings (n = 1 ‘good’, n = 1 ‘fair’ quality). Most studies suggested that increased sleep apnoea severity was associated with an increased MVC risk. Furthermore, untreated sleep apnoea was predominantly associated with increased risk, whilst decreased risk was associated with Continuous Positive Airway Pressure (CPAP) and uvulopalatopharyngoplasty (UPPP) treatments. Five studies (n = 3 ‘good’, n = 2 ‘fair’ quality) investigated MVC risk associated with disorders of hypersomnolence and narcolepsy, and all reported increased risk. Only two studies investigated MVC risk associated with insomnia, with inconsistent findings: one reporting increased MVC risk (‘good’) and one reporting no difference (‘fair’). Regarding impacts on on-road driving test outcome, our comprehensive search found no studies investigating the association between sleep disorders and this driving safety outcome measure. Notwithstanding the limitations of the included studies, the weight of evidence suggests a moderately elevated MVC risk for drivers with sleep disorders (sleep apnoea; hypersomnia and narcolepsy), with the majority reporting around two and a half times higher risk, and lower risk with treatment. This evidence is consistent with current fitness-to-drive guidelines, most of which specify licence restrictions conditional upon severity, treatment compliance and effective response to treatment. The generalisability of the findings is limited as many identified studies had methodological limitations, were conducted across a wide time period, in numerous licensing jurisdictions with different requirements, and across a diverse range of participant populations. A large-scale, population-based controlled study, in multiple licensing jurisdictions with equivalent licensing and fitness-to-drive requirements, is warranted to rigorously investigate MVC risk and sleep disorders, including evaluating the possible benefit of therapies.     

Exploring the association of the Comprehensive Trail Making Test with driving indexes in patients with Parkinson’s disease

The Trail Making test (TMT) has been identified as predictor of driving ability in patients with Parkinson’s disease (PD). However, previous research has not explored the effectiveness of an alternative version of the TMT, namely of the Comprehensive Trail Making Test (CTMT; Reynolds, 2002) to show associations with measures related to driving fitness. Main objective of the current work was to evaluate the capacity of the CTMT to detect associations with fitness to drive related measures in patients with PD. Inclusion criteria were the presence of a valid driver’s license, regular car driving, a CDR score ≤ 0.5, and a Hoehn & Yahr score between 1 and 3. Twelve individuals with PD (Age: Mean = 63.75, SD = 10.50) and 12 cognitively intact individuals (Age: Mean = 63.50, SD = 10.43) were introduced in the study. Collection of data included a comprehensive neurological/neuropsychological assessment and a driving simulation experiment. Certain subtests of the CTMT were more strongly associated with a variety of driving indexes in individuals with PD as compared to the original TMT. In addition, according to the stepwise regression models that were applied, the CTMT was recognized as a more effective predictor of driving behavior than the TMT. The pattern of findings that was observed supports the usefulness of CTMT on detecting associations with fitness to drive related-measures in patients with PD. Underlying factors that may explain the effectiveness of the CTMT could be related to the greater variety of set shifting and inhibition processes that this alternative option integrates as compared to the original TMT.