Older driver estimates of driving exposure compared to in-vehicle data in the Candrive II study

Most studies on older adults’ driving practices have relied on self-reported information. With technological advances it is now possible to objectively measure the everyday driving of older adults in their own vehicles over time. Objective. The purpose of this study was to examine the ability of older drivers to accurately estimate their kilometers driven over one year relative to objectively measured driving exposure. Methods. A sub-sample (n=159 of 928; 50.9% male) of Candrive II participants (age ≥ 70 years of age) was used in these analyses based on strict criteria for data collected from questionnaires as well as an OttoView-CD Autonomous Data Logging Device installed in their vehicle, over the first year of the prospective cohort study. Results. Although, there was no significant difference overall between the self-reported and objectively measured distance categories, only moderate agreement was found (weighted kappa = 0.57; 95% CI 0.47 to 0.67). Almost half (45.3%) chose the wrong distance category, and some people mis-estimated their distance driven by up to 20,000 km. Those who misjudged in the low mileage group (≤ 5,000 km) consistently under-estimated, while the reverse was found for those in the high distance categories (≥ 20,000), i.e., they always over-estimated their driving distance. Conclusions. Although self-reported driving distance categories may be adequate for studies entailing broad group comparisons, caution should be used in interpreting results. Use of self-reported estimates for individual assessments should be discouraged.The CIHR Team in Driving in Older Persons (Candrive II) Research Program #9042