Injuries and hospital admissions involving sharable two-wheeled electric scooters are on the rise in the U.S., a new study finds.

Most concerning, researchers say, is that nearly a third of patients showing up at hospitals after an accident involving the powered, standing scooters had a head injury.

“While most people recover from head injuries, there is going to be a subset with long term disability and life changes,” said coauthor Dr. Benjamin Breyer of the University of California, San Francisco. “I would like people to be aware of the risks and protect themselves.”

It probably shouldn’t be a surprise that people are turning up in EDs with injuries associated with electric scooters, Dr. Breyer said. “The market was flooded with these scooters,” he said.

One big problem is that riders often don’t wear helmets, Dr. Breyer said. And it’s not clear how to fix that problem because the decision to take an e-scooter can be spur of the moment, he added.

Although concerned about injuries, Dr. Breyer isn’t anti-scooter.

“I think it’s a great way to promote active commuting and get people out of their cars,” he said.

To take a closer look at the rate of injuries around the nation involving electric scooters, Dr. Breyer and colleagues turned to the National Electronic Injury Surveillance System (NEISS), which provides estimates of the number of injured people turning up at U.S. emergency rooms based on a sample of hospitals.

As reported in JAMA Surgery, the researchers discovered that e-scooter injury rates had increased dramatically in just four years: the incidence more than doubled during those years, rising from 6 per 100,000 in the population to 19 per 100,000.

Of the estimated 14,651 e-scooter-related injuries in 2018, 4,658, or 32 percent, involved the head. Upper extremity injuries totaled 3,747 in 2018, up more than three-fold from 1,083 in 2014, while lower-extremity injuries also rose nearly three-fold from 1,721 to 4,707.

People ages 18 to 34 were the most likely to sustain e-scooter injuries. During the study period, hospital admissions in this age group skyrocketed, rising by 354 percent.

Dr. Breyer points to a 2019 analysis of data from two hospitals in Southern California, which found just 4.8 percent of injured e-scooter riders were wearing helmets.

A coauthor of that study believes her paper and this new one probably underestimate how many injuries are occurring.

For one thing, “most doctors probably don’t even know that there is a code for injuries that are scooter related,” said Dr. Joann Elmore, a professor of medicine at the University of California, Los Angeles, who wasn’t involved in the current study. And the studies “don’t include the likely more common and more numerous outpatient visits to primary care providers.”