The role of reduced fitness to drive due to medical impairments in explaining crashes involving older drivers.

BACKGROUND Medical conditions and associated impairments are known to be more prevalent with aging and can potentially impact the function and crash risk of older drivers. OBJECTIVES To evaluate the impact of specific medical conditions and associated impairments on older driver crash risk. METHODS A search identified reports and peer-reviewed publications evaluating the risk for medical conditions and associated crash risk. Medical conditions associated with older persons were reviewed to determine the associated relative risk of crash. RESULTS The review identified three recent comprehensive reviews of medical conditions or chronic illnesses and crash risk: Dobbs (2005); Vaa (2003); Charlton et al. (2004). Comparison of the reviews reveals a relatively high agreement where medical conditions considered to be at slightly to moderately increased relative risk of crash include alcohol abuse and dependence, cardiovascular disease, cerebrovascular disease/TBI, depression, dementia, diabetes mellitus, epilepsy, use of certain medications, musculoskeletal disorders, schizophrenia, obstructive sleep apnea, and vision disorders. However, determining fitness to drive at the individual level based on diagnosis has significant limitations related to factors such as multiple medical conditions as well as varying severity of disease and associated functional impairments. Medical conditions that may affect driving can serve as "red flags" to assist health care professionals and driving administrators to identify drivers who may need further evaluation. CONCLUSIONS Medical conditions overall, do impact the fitness to drive of older drivers; however, the crash risk tends to be only slightly to moderately increased. The conditions can serve as potential warnings for reduced fitness to drive, but many persons with these medical conditions would still be considered safe to continue driving.