Across a number of research paradigms, including use of self-reported driving histories, driving simulators, and on-the-road driving evaluations (Fitten et al. 1995
; Odenheimer et al. 1994
; Rebok et al. 1995
; Rizzo et al. 1997
), neurocognitive deficits have been associated with declines in driving ability. Evidence suggests that as many as 29% of HIV-infected subjects report a decline in driving ability (Marcotte et al. 2000
), and there appears to be a higher likelihood of both poorer driving simulator performance and real world driving ability (i.e., being cited for a moving violation or being involved in a motor vehicle accident during the previous year) among HIV+ individuals demonstrating neuropsychological impairment (Marcotte et al. 2000
). Importantly, both neuropsychological ability and poor driving simulator performance have been predictive of real world driving difficulties (Marcotte et al. 2001
), suggesting that laboratory-based tasks may be useful in detecting real world functional capacity.
The earliest research investigating the effects of neuropsychological impairment upon driving capacity in HIV-infected individuals (Marcotte et al. 1999
) revealed that those classified as mildly cognitively impaired failed driving simulations at a rate five to six times greater than cognitivelyintact participants, and neuropsychological performances in attention and working memory, fine motor abilities, visuo-constructive abilities, and nonverbal memory, were predictive of various components of driving ability. Marcotte and colleagues (2004)
later utilized a comprehensive neuropsychological test battery and two driving simulations (on-the-road driving evaluation, and a task of visual processing and attention: Useful Field of View Test
) to assess both navigational abilities and evasive driving. Results indicated that neuropsychologically-impaired HIV+ participants had increased simulator accidents and reduced simulator driving efficiency, failed on-road driving tests at a higher rate, and demonstrated decreased visual processing and divided attention when compared to cognitively-intact HIV+ and control participants. Moreover, global neuropsychological functioning, simulator accidents, and simulator driving efficiency accounted for 47.6% of the variance in on-road driving performance, with executive functioning emerging as the only significant neurocognitive predictor of on-the-road driving failure rates.
A more recent study conducted by Marcotte and colleagues (2006)
utilized Useful Field of View performances, neuropsychological status, and detailed self-reported driving history (see ). Among the HIV+ sample, 45% evidenced at least mild cognitive impairment compared to only 5% of the control participants. HIV+ participants also demonstrated a far higher rate of abnormal divided attention when compared to control participants (36% vs. 17%, respectively). Not only did poor attention predict self-reported accidents, but 93% of the HIV+ participants who acknowledged prior automobile accidents were correctly classified when poor attention and general neuropsychological impairment were considered simultaneously.
Fig. 3 Accidents per Million Miles in Past Year for HIV+ Groups Stratified by Neuropsychological Impairment and Risk Level*. Note: Adapted from Marcotte, T.D., Lazzaretto, D., Scott, J.C., Roberts, E., Woods, S.P., Letendre, S., & the HNRC Group. (2006). (more ...)
Taken together, these studies suggest that neurocognitive compromise among HIV-infected adults is strongly associated with impaired driving capacity across a variety of driving paradigms. This body of work extends the well-substantiated findings of reduced cognitive capacity among HIV-infected individuals (e.g., divided attention, visual attention and visual processing, and executive function), and provides support for relationships between these neurocognitive deficits and poor simulator performance, self-reported driving problems, and importantly, real world driving decrements. These results appear to be relevant even for HIV-infected individuals presenting with only mild levels of neurocognitive compromise, suggesting a relatively low cognitive impairment threshold for poor functional ability.
Driving capacity is an especially important concern for older HIV-positive adults due to the additional safety concerns posed by the additive effects of the aging and the HIV disease process. Recent studies have begun to address driving performance among this unique subgroup. Lee et al. (2003a)
found that poor simulated driving performance explained over two-thirds of the variability in actual on-road driving in a group of elderly adults (aged 60 and older). Similar findings have been reported in other studies, including those in which specific cognitive abilities were assessed via driving simulation tasks, including working memory (Lee et al. 2003b
), visual attention (Lee et al. 2003c
), and divided attention (Brouwer et al. 1991
A recent study conducted by our laboratory (Gooding et al. 2008
) revealed that the driving performances of older HIV-infected adults (age>50) on a route-planning virtual city task were significantly less efficient and slower than for younger HIV-infected adults (age<40). To explore the basis for this finding, driving simulator performance was regressed on neuropsychological test performance. For the older adults, neuropsychological test scores accounted for 44% of the variance on task completion time and 50% of the variance on efficiency of route. However, for younger adults, neuropsychological test scores accounted for only 1% of the variance on both measures of simulator performance. Both visuospatial abilities and attention independently predicted driving simulator performance on these driving efficiency and speed variables for the older group only. The results of this study suggested that older HIV-infected adults may be at increased risk for functional compromise secondary to HIV-associated neurocognitive decline, and attention and visuospatial abilities constitute the neurocognitive domains maximally predictive of driving simulator performance. Driving is a highly demanding and potentially hazardous daily activity and these findings suggest that older HIV-infected adults demonstrating reduced visuospatial and attentional abilities may be at particular risk for impaired driving ability.
Of the methodologies employed to date to investigate driving capacity in HIV-infected individuals at risk for impaired driving performance, driving simulator tasks and on-the-road driving evaluations appear to align most closely with real world driving ability. Although a specific neuropsychological profile indicative of poor driving has not yet been identified, the aforementioned studies suggest strong relationships between reduced driving performance and neurocognitive decrements across a variety of domains among HIV-infected subjects. Deficits in visual attention, visuospatial ability, memory, fine motor control, and executive function likely contribute most notably to reduced driving performance among HIV-infected individuals, with visuospatial and attentional abilities playing a particularly key role among older HIV-infected adults.