More Americans are reaching for bicycles for quick workouts or to replace cars for daily commutes, an encouraging sign for public health -- and the environment. But as they do, the rate of cycling-related injuries and hospital stays in the U.S. is steadily climbing. Both rose sharply between 2008 and 2013, according to data published Tuesday by the Journal of the American Medical Association. And older Americans are feeling more of the pain.

There’s ample evidence to support the health benefits of cycling, which has been shown to improve cardiovascular fitness and make it easier to maintain a healthy weight. These perks have persuaded more Americans to take to the road -- the number of people who had ridden a bicycle in the past year rose from 47 million in 2008 to 67 million in 2014 -- a 70 percent increase.

But new research by a team of scientists from the University of California San Francisco shows that the rate of bicycling-related injuries and hospital stays is also steadily growing, which could be a sign that the nation’s enthusiasm for cycling is outpacing safety efforts and urban improvements such as designated bike lanes to protect users. Perhaps most notably, U.S. Secretary of State John Kerry broke his femur this year in a cycling accident in France.  

The researchers searched a database that compiles data from 100 emergency departments across the country for bicycling-related injuries from 1998 to 2013. Over that period, the number of cyclists who were injured in an accident increased by 28 percent. The rate of injuries rose from 96 per 100,000 cyclists to 123 per 100,000 cyclists during those 15 years. At the same time, the rate of hospitalizations among cyclists rose by 120 percent, from about five hospital stays per 100,000 cyclists in 1998 to 11 by 2013.

Much of the increase is due to the fact that more people are riding bikes -- bicycle commuting grew 47 percent over the past decade, according to the bicycle advocacy group People for Bikes. But the authors also point out that since the rate of hospitalizatons grew faster than the rate of injuries during their study, cyclists may also be suffering more severe injuries. Overall, the number of cyclists who are involved in accidents remains a small fraction of those who take to the road.  

Older Americans seem to be driving the trend, which reflects previous data showing they have taken up cycling at a faster rate than other age groups. Of all those cyclists who sustained bicycling-related injuries, the proportion of Americans over 45 years old who were harmed while riding jumped from 23 percent in 1998 to 42 percent in 2013. The proportion of hospital admissions for this group also grew substantially. By 2013, older cyclists were responsible for 65 percent of bicycling-related hospital stays. The authors suggest that further investment in cycling infrastructure and safety outreach may serve these riders in particular.