Biking is a wonderful way for older adults to get exercise because it offers cardiovascular benefits without adding strain to aging joints. But older riders should always be on guard. The number of bicycle accidents among people 45 and older has surged. And when an older adult has an accident, the injuries are usually far more severe than for a younger rider in a similar accident.

"These are people who come to the emergency room and it's significant enough that they are admitted for tests or further treatment," says Dr. Benjamin Breyer, a professor at University of California San Francisco School of Medicine. Breyer was senior author on a new study that found that riders 45 and older accounted for 42 percent of all bike injuries in 2013, up from 23 percent in 1998. Additionally, 65 percent of riders admitted to hospitals because of bike injuries were 45 and older, up from 39 percent in 1998.

There is no actual number of how many bicyclists suffer injuries, but the Centers for Disease Control and Prevention estimates that 550,000 Americans go to the emergency room each year because of a bike accident. About 30,000 of the injuries are serious enough to require hospital admission.

Breyer, also chief of urology at San Francisco General Hospital and Trauma Center, says it's not just recreational bikers who end up in the hospital. "More people are riding at higher speeds for sports, along the line of what a competitive cyclist does," he says.

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You can lower your risk of sustaining a serious injury. The National Highway Traffic Safety Administration says wearing a helmet is "the single most effective way" to prevent head injury if you have a bicycle accident. Also wear reflective or brightly colored clothing so drivers can see you better from a distance. This is especially important at dusk: More bicyclists are killed during the hours 6-9 p.m. than any other period of the day. You can download a booklet on bike safety for adults from the NHSTA at nwsdy.li/bikesafety.

Despite the daunting statistics, the last thing Breyer wants is for his study to scare older adults away from biking. "Biking is a tremendous way to keep youthful, healthful and happy. The benefits far outweigh the risks," he says. "Maybe data like this can help people remember to be safe."