Drivers over age 80 or women over age 70 who take the prescription sleeping pill Ambien tend to have more motor vehicle collisions, according to a new study.

Studies in younger drivers have also shown a link between Ambien, known generically as zolpidem, and motor vehicle collisions, said lead author John N. Booth III, of the University of Alabama at Birmingham.

The new data, however, extend the findings to show that "older adults, specifically women older than 80 years, have significantly higher odds of motor vehicle collisions while talking zolpidem," Booth told Reuters Health by email.

The researchers used information from a study of 2,000 current drivers age 70 or older living in Alabama.

The drivers reported their gender, race, marital status, retirement status, current occupation or occupation prior to retirement, alcohol and tobacco intake and chronic medical conditions via questionnaires. They also completed a driving habits questionnaire and brought any prescription or over-the-counter medications to a clinical visit so researchers could review the pill bottles.

About 4 percent of participants were using zolpidem. These individuals tended to have more chronic health conditions, more falls over the previous year, to be taking more medications, and to drive fewer miles annually than the rest of the group.

Using accident police reports from the previous five years, the researchers found that overall, motor vehicle collision rates were similar for zolpidem users and nonusers when other factors were accounted for. But specifically among women, crashes were 61 percent more likely for zolpidem users. And among drivers over age 80, those using zolpidem were more than twice as likely to have been in a car accident in the last five years, the authors reported in Sleep Medicine.

When men and women take the same dose of zolpidem, the women tend to have higher concentrations of the drug in their plasma, which may help explain the results, Booth said.

"Like motor vehicle collisions, sleep problems are a significant health problem for older adults," Booth said. "Balancing the risks associated with elevated motor vehicle rates with the adverse health outcomes associated with poor sleep is a complicated issue that must take into account the broader perspective of a patient's overall health."

A spokeswoman for Sanofi, Ambien's manufacturer, said the company treats zolpidem reports with the highest degree of importance, and patients should only take the medication as directed by a physician.

"We stand behind the robust clinical data that have demonstrated the safety and efficacy of this product since its approval in the U.S. in 1992, representing more than 20 years of real-world use and 24 billion nights of patient therapy worldwide," the spokeswoman told Reuters Health by email. "The U.S. FDA-approved label states do not take zolpidem unless you are able to stay in bed a full night (7-8 hours) before you must be active again."

Other sedative hypnotic medications such as trazodone (Oleptro) and temazepam (Restoril) have also been associated with higher car accident risk, Booth said.

"In 2013 the FDA recommended that physicians prescribe low doses of sedative hypnotics," he said. "This was a response to recent findings that high concentrations of this type of medication can remain in the bloodstream after awakening in the morning to interfere with driving."

For older people taking zolpidem, being aware of the side effects could minimize motor vehicle risk, he said.

"For persons taking zolpidem, driving after they have been awake for an extended period of time can help the sedative to become metabolized and have a lower concentration in the blood," Booth said.

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