Drivers with dementia: Forecasting the future

Abstract

BackgroundA decline in driving skills is well documented in people with dementia.ObjectiveTo provide a current estimate and future forecast of drivers with dementia in Ontario, Canada, taking into account sex differences and longitudinal estimates of driving cessation in dementia.MethodsWe used historical provincial licensing data, population estimates and projections, as well as estimates of diagnosable dementia from the Landmark study of the Alzheimer's Society of Canada to create current estimates and forecasts of drivers with dementia in the province of Ontario, the most populous province of Canada, from 2024 to 2046. Sensitivity analyses were used to determine the impact of sex and assumptions regarding the rate of driving cessation.ResultsAssuming that an estimated 35% of people with diagnosable dementia stop driving very shortly after symptom onset followed by a more gradual decline over time, and that females stop driving twice as fast as men, we forecast approximately 154,000 drivers with dementia in the province of Ontario in 2046.ConclusionsAs dementia prevalence increases, our study provides a novel set of projections for drivers with dementia over the coming two decades, estimating a 221% to 226% increase. This work adds to the myriad of concerns about health and public services that will be needed to treat and support this population effectively, to detect early signs of dangerous driving among the cognitively impaired, and to provide alternative transportation options, once driving is no longer viable.

Keywords: Alzheimer's disease; automobile driving; dementia; epidemiology.

Figure 1.

The forecasted number of drivers in Ontario from 2024 to 2046 of (a) ages 40 and over or; (b) ages 80 and over. We show the yearly numbers of licensed males and females, which sum to the total licensed population.

Figure 2.

The number of licensed drivers in Ontario with diagnosable dementia in the following scenarios: i. Least conservative estimate, assuming all drivers with DD experience driving cessation following survival curve reported in Herrmann et al.; ii. Best estimate, assuming both male and female populations experience an additional 35% cessation prior to the cessation from the survival curve reported in Herrmann et al.; ii 25%. Sensitivity analysis on the best estimate, assuming both male and female populations experience 25% cessation prior to the cessation from the survival curve reported in Herrmann et al.; ii 45%. Sensitivity analysis on the best estimate, assuming both male and female populations experience 45% cessation prior to the cessation from the survival curve reported in Herrmann et al.; iii. assuming both male and female populations experience an additional 35% cessation prior to the cessation from the survival curve reported in Herrmann et al., and females cease driving at 2x the male rate, and; iv. Most conservative estimate, assuming males and females all cease driving within 1 year of acquiring diagnosable dementia.

Figure 3.

Disaggregation of “best estimate” forecast by gender. Estimate shown is the number of licensed drivers with diagnosable dementia assuming both male and female populations experience an additional 35% cessation prior to the cessation from the survival curve reported in Herrmann et al.

Figure 4.

The number of licensed drivers with diagnosable dementia in the “best estimate” scenario, broken down by age and gender (left panel for males, right panel for females).