As Use of Shared Bikes and Scooters Spreads, So Do Head Injuries

In more than 200 U.S. cities, shared e-bikes, e-scooters and bicycles are just a tap away on a smartphone. They’ve become a common sight — not just in major metros like New York or Los Angeles but also in midsize cities and college towns. Wherever these easy-to-grab-and-go devices show up, injuries follow, many involving the brain. 

A growing body of research, including a recent study in the journal Neurosurgery, finds that crashes involving bikes and scooters are sending more people to emergency rooms with head injuries. Older adults are doing plenty of the riding — or getting hit — and face higher risks of serious complications.

“Older age was associated with higher [hospital] admission rates, higher intensive care unit (ICU) admission rates and longer hospital stays,” says Dr. Hannah Weiss, a neurosurgery resident at NYU Langone Health and lead author of the Neurosurgery study. 

“There’s a responsible way to enjoy getting around a city on a bike or a scooter,” Weiss says. “It comes down to making a couple of wise choices.” Here’s what to know about your risk and how you can protect yourself, whether you’re riding or walking by.

Where there are bikes, there are brain injuries

The study, published in April in Neurosurgery, was based on trauma cases treated at Bellevue Hospital, a Level 1 trauma center in New York City. The injuries tied to bikes and scooters, which rose sharply in recent years, mirrored the growing use of these personal vehicles. Among people coming into the hospital after bike or scooter crashes, about 1 in 3 had a traumatic brain injury (TBI) — a rate high enough to concern the neurosurgeons who conducted the study. 

In this study, here’s how the doctors defined a TBI: any injury inside the skull that could be seen on a CT scan, like bruising, swelling or bleeding. These could be caused by falls and even seemingly minor blows to the head. Some concussions, even mild ones, cause injury that’s visible on a scan. People are often surprised that concussions are also considered TBIs. 

“We were seeing a huge uptick in the number of patients we were being called about with injuries related to bike or scooter accidents,” Weiss says. And the riders weren’t the only ones at risk. Pedestrians struck by these devices fared even worse: More than half experienced a TBI. 

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Overall, Weiss says, “patients with more severe outcomes tended to be older.” The average age of those who ended up in the ICU was about 45, while those who avoided critical care averaged 40 years old. 

No matter how fit or healthy you are, Weiss says, as you get older and your brain loses volume as a natural part of the aging process, you become more prone to a traumatic brain injury.

“An older individual might have a little more space in their head,” Weiss says. When there’s room, a blow to the head can shake the brain inside the skull. “Your brain moving around can cause a concussion or bruises on the brain and tear small vessels, which leads to brain bleeds.” 

The study also found that injuries were more common during busy evening hours and often involved people who were not wearing helmets. Taken together, the findings suggest that as use of scooters, bikes and e-bikes becomes more common on crowded streets, the risk of serious head injury is rising too. 

It’s not only a New York City problem

The Neurosurgery study calculated injuries in one of the city’s main trauma centers, but this isn’t just a New York City problem. A separate national study published in 2024 in the American Journal of Public Health found that injuries linked to ride-on devices have risen sharply across the United States.

“Bike safety is a major public health concern,” says Kathryn Burford, lead author of the 2024 study and a postdoctoral research assistant at Columbia University Mailman School of Public Health. 

Using a national sample of emergency department visits taken from 96 hospitals across the U.S., Burford and colleagues estimated nearly two million injuries involving bikes, e-bikes and e-scooters occurred between 2019 and 2022, with rates climbing steeply during that time, particularly for e-bikes and scooters.