Evaluating the crash and citation rates of Utah drivers licensed with medical conditions, 1992-1996.
BACKGROUND
Medical problems may affect the ability to drive motor vehicles, and programs that control the issuing of driver licenses to individuals with medical conditions exist in most states. The main activity of these programs is the imposition of restrictions upon the driving privileges of individuals with medical conditions that are deemed to pose some risk to public safety. However, little is known about the effectiveness of these licensing programs.


OBJECTIVE
The objective of this study was to compare the rates of adverse driving events (crash, at-fault crash and citations) experienced by drivers licensed with medical conditions to those of age-, sex- and location-matched controls. Separate comparisons were made for drivers reporting medical conditions licensed with full driving privileges, and those with restricted driving privileges (e.g. speed, area and time of day).


METHODS
Retrospective case-control.


METHODS
The study population was all drivers licensed in the state of Utah who reported a medical condition on their driver license application, over the 5-year period 1992-1996. Drivers enter the program by self-reporting their medical problems. Control drivers were chosen from the entire population of drivers licensed in Utah for the same period. Information on driver license status, participation in the medical conditions program, citations, involvement in crashes, and death certificate data was obtained from the relevant state agencies. Probabilistic linkage methodology was used to link the records in these disparate databases for eventual analysis. Rates of citation, crashes and at-fault crashes, expressed as events per 10000 license days, were calculated separately for program drivers and their corresponding control groups for each medical condition category and restriction status. These data were used to determine an estimate of relative risk (RR) and 95% confidence intervals.


RESULTS
As a group, medical conditions drivers had modestly elevated rates of adverse driving events compared with control drivers (RR 1.09-1.74). Rates in the largest medical category, 'cardiovascular conditions', were not higher than controls. Rates were higher than control for some conditions, such as 'alcohol' and 'learning and memory', for some adverse events (RR 2.2 -5.75). Drivers with more than one medical condition appeared comparable to the general group of medical conditions program drivers.


CONCLUSIONS
Drivers in Utah medical conditions program had modestly elevated rates of adverse driving events compared to matched controls. Possible underreporting of medical conditions and accurate assessment of exposure rates are potential weaknesses in the program.
Vernon
Donald D
DD
University of Utah School of Medicine, Salt Lake City 84108, USA. don.vernon@hsc.utah.edu
Diller
Edma M
EM
Cook
Lawrence J
LJ
Reading
James C
JC
Suruda
Anthony J
AJ
Dean
J Michael
JM
D000063:Accidents, Traffic / Q000706:statistics & numerical data*; D002318:Cardiovascular Diseases; D016022:Case-Control Studies; D006304:Health Status; D006801:Humans; D008659:Metabolic Diseases; D009422:Nervous System Diseases; D014589:Utah