Association between polypharmacy and hard braking events in older adult drivers

Background: Polypharmacy (i.e., simultaneous use of two or more medications) poses a serious safety concern for older drivers. This study assesses the association between polypharmacy and hard braking events in older adult drivers. Methods: Data for this study came from a naturalistic driving study of 2990 older adults. Information about medications was collected through the “brown-bag review” method. Primary vehicles of the study participants were instrumented with data recording devices for up to 44 months. Multivariable negative binomial model was used to estimate the adjusted incidence rate ratios (aIRRs) and 95 % confidence intervals (CIs) of hard-braking events (i.e., maneuvers with linear deceleration rates ≥0.4 g) associated with polypharmacy. Results: Of the 2990 participants, 2872 (96.1 %) were eligible for this analysis. At the time of enrollment, 157 (5.5 %) drivers were taking fewer than two medications, 904 (31.5 %) were taking 2–5 medications, 895 (31.2 %) were taking 6–9 medications, 571 (19.9 %) were taking 10–13 medications, and 345 (12.0 %) were taking 14 or more medications. Compared to drivers using fewer than two medications, the risk of hard-braking events increased 8 % (aIRR 1.08, 95 % CI 1.04, 1.13) for users of 2–5 medications, 12 % (aIRR 1.12, 95 % CI 1.08, 1.16) for users of 6–9 medications, 19 % (aIRR 1.19, 95 % CI 1.15, 1.24) for users of 10–13 medications, and 34 % (aIRR 1.34, 95 % CI 1.29, 1.40) for users of 14 or more medications. Conclusions: Polypharmacy in older adult drivers is associated with significantly increased incidence of hard-braking events in a dose–response fashion. Effective interventions to reduce polypharmacy use may help improve driving safety in older adults.