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Single drink can impair drivers aged 50 and older, study finds

Even a single drink impairs an older person’s ability to control the steering wheel and maintain a consistent speed.

Single drink can impair drivers aged 50 and older, study finds
The study found that the small, legal levels of alcohol had a significant effect on the driving skills of the older drivers.

Baby boomers take note: Adults aged 50 and older are more susceptible to the effects of alcohol — even a single drink — on their driving abilities than younger adults in their 20s and 30s, according to a small study published recently in the journal Psychopharmacology.

Other research has found that age alone tends to have a negative effect on driving skills, particularly among drivers over the age of 65. This new study suggests that the consumption of alcohol, even at low levels, exacerbates that negative effect.

Yet, older people are usually unaware that their bodies have become more sensitive to alcohol.

“Unfortunately, the subtle change in the effects of alcohol on performance over time may lead older adults to ignore these risks as they are unlikely to have experienced significant consequences or impairment resulting from this level of consumption at earlier points in their lives,” write the study’s authors.

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Changing demographics make this finding particularly worrisome. Americans are living — and driving — longer. Between 1999 and 2009, the number of licensed drivers over the age of 65 jumped 20 percent, to 33 million, according to the American Automobile Associaiton (AAA). By 2030, 70 million Americans will be aged 65 and older, and 85 percent to 90 percent of them will have drivers licences, the AAA adds.  

Study used a driving simulator

For the study, researchers at the University of Florida recruited 36 older (aged 55 to 70) and 36 younger (aged 25 to 35) adults. All were healthy and reported being moderate social drinkers.

Both groups were brought into a lab, where they undertook a simulated driving test. The test was a relatively simple one. It involved “driving” down a winding, three-mile stretch of a two-lane country road. Other than an occasional oncoming car, the route involved no visual distractions. To control the car, the participants had a steering wheel and accelerator and brake pedals.

The researchers measured several components of driving ability during the test, including how quickly the driver was able to adjust the steering wheel to the turns in the road, how well the driver kept the car in its lane, and how well the driver maintained a constant speed. They also calculated the driver’s average speed along the three-mile route.

A few days later, the participants were brought back to the lab and asked to repeat the simulated driving test. This time, each age cohort was divided into three groups. Two of the groups drank a lemon-lime soda spiked with enough alcohol to produce a blood alcohol concentration (BAC) of either 0.065 percent or 0.04 percent. The third group drank the same beverage “misted” with a negligible amount of alcohol. (This was the placebo group.)

The groups that drank the alcohol still had BACs below 0.08 percent, the federal legal limit for driving under the influence.

Less control over steering and speed

The study found that the small, legal levels of alcohol had a significant effect on the driving skills of the older drivers. In particular, they were less able to control the steering wheel and to maintain a constant speed after consuming alcohol than when sober.

That was not true of the younger drivers. The amount of alcohol consumed in the study had a “negligible” effect on their driving skills, although it did increase their average speeds. (Both age groups tended to stay within the test’s 55-mile-per-hour speed limit, however.)

This finding regarding the younger drivers should be interpreted cautiously, warn the study’s authors, because the driving task used in this research was a relatively simple one, and it did not involve real-life driving.

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Other research has shown that BACs as low as 0.02 percent affect the ability of people of all ages to visually track a moving object and to perform two tasks at the same time — skills required for safe driving.

The researchers plan to continue their research using more complex driving tasks.

You can read the study in full online.