What Factors Affect Driving Ability with Aging?

Driving ability is not simple to assess. It is a complex skill affected by multiple factors, including physical health, mental health, and the quality of the driving environment, such as road conditions and signage.

The Three Functions of Driving

Age-related changes in body and mind can affect driving abilities in three functional areas. Drivers must have the ability to:

1. See traffic and road conditions
2. Cognitively (mentally) recognize these images, process what they recognize, decide how to react to the situation
3. Perform the physical movement required to control the vehicle²⁴

Age-related changes can affect any one of these functional areas. Visual, cognitive and physical problems can occur at any age and complicate the driving task. Some visual impairments, such as declines in night vision, may occur as young as age 40.²⁵ When assessing a driver's crash risk, functional impairments that affect driving are important to consider.

Aging is associated with multiple changes in sensory and perceptual capabilities. Investigating these changes opens possibilities for accommodations that can increase driving life expectancy. The changes that take place during the aging process commonly affect at least one of the following areas:

• Sensory perception
• Cognition
• Physical and psychomotor function
  Some conditions, such as diabetes, affect multiple functions. Polypharmacy, the use of multiple medications, may also affect multiple functions. Studies suggest that at least seven out of ten people ages 65 and older use prescription medications. People over 65 make up 13 percent of the U.S. population, yet they account for 34 percent of all prescription medications dispensed, and 30 percent of over-the-counter (nonprescription) medications purchased.^26,27

Additionally, the use of alcohol can alter the body's reaction to the medications, throwing in another factor that can change multiple functions in the body.

²⁴ Kaplan, W. (1999) "The occupation of driving: legal and ethical issues." Physical Disabilities Special Interest Section Quarterly 22(3):1. Bethesda, MD: American Occupational Therapy Association.

²⁵ Ibid.

²⁶ Cameron, K.A. (1997) "Over the Counter and into the Home." United Seniors Health Cooperative Special Report 48:5-7.

²⁷ Families USA Report (2000) "Cost Overdose: Growth in Drug Spending for the Elderly 1992-2010." Washington, DC: Families USA.