Banner -- Identifying Strategies to Collect Drug Usage and Driving Functioning Among Older Drivers


Polypharmacy is the use of many medications at the same time. Other definitions include prescribing more medication than is clinically indicated, a medical regimen that includes at least one unnecessary medication, or the empiric use of five or more medications (Michocki, 2001). Lee (1998) notes that the definition of polypharmacy is controversial, with authors disagreeing on the number of drugs—varying from study to study, from the concomitant use of more than 2 drugs, 4 drugs, 5 drugs, 6 drugs, and 10 drugs—and whether to include as-needed medications, over-the-counter drugs, or herbal and alternative medications.

Within the context of the present NHTSA research on polypharmacy and older drivers, it is instructive to consider findings by Hébert, Bravo, Korner-Bitensky, and Boyer (1996) that the consumption of three or more drugs per day increases the risk of functional decline in elderly people by 60 percent (cited in Allard et al., 2001).

The risks of polypharmacy include an increase in the number of potentially inappropriate prescriptions (PIP), cognitive disorders, falls, hip fractures, depression, and incontinence (Gurwitz, Soumerari, and Avorn, 1990). Additionally, preliminary results of a project currently underway for NHTSA suggest that there is an increased risk of motor vehicle crashes for older drivers who use multiple potentially driver-impairing medications (LeRoy, 2004). Wilkinson and Moskowitz (2001) reviewed 21 studies of multiple medication use by the community-dwelling older population in the United States and found that approximately 10 to 27 percent of community-dwelling elderly are prescribed medications on the Beer’s List of Drugs that are potentially inappropriate for people over age 65. Medications on this list are deemed inappropriate because they are either ineffective or the potential for adverse outcomes is greater than the potential for benefit. Allard et al. (2001) reported on a study performed by the Quebec Health Insurance Board (1992), which found that approximately 10 percent of the elderly population of Quebec has at least one PIP that meets the criteria for therapeutic overlapping, a high daily dose, or a harmful drug interaction. The Quebec Health Insurance Board further found that the PIP risk increases exponentially with the number of drugs. For example, taking fewer than 4 drugs is associated with a 12 percent risk, whereas taking more than 5 drugs a day involves a 40 percent PIP risk. It is important to note that the prevalence of potentially driver-impairing medications in the community-dwelling population of older people is likely higher, given that many drugs not on the Beers list can impair safe driving performance.

This section of the report will describe: (1) the prevalence of prescription and over-the-counter medication use by older community-dwelling people in the United States and in other countries; (2) how these frequently used medications interact with the aging body; (3) the consequences of medication use on older person’s ability to drive safely; and (4) the consequences of medication use on falls and other adverse events.