A group of researchers from Canada and the United States interested in correlations between brain trauma and bike shares discovered a 14 percent greater risk for bike-related brain traumas in cities that had such programs compared to cities without bike shares.
Before bike shares, brain-related injuries made up 42.3 percent of these cities' injury pie. Afterward, they made up 50.1 percent. The study doesn't imply that cyclists were injured more often, but that comprehensively, brain-related injuries are making up a larger portion of total injuries.
The researchers used a control group of cities without bike-share programs, such as Seattle and Minneapolis, which saw no change in brain trauma admissions, at 35.9 percent.
"The study basically confirmed our worries," said Janessa Graves, lead author of the study published Thursday, in an interview with NPR. "Public bike-share initiatives are great wellness initiatives … But without providing helmets, we were concerned that we would see an increase in head injuries. And we did."
It's important to recognize that the study's interpretations don't account for a lot: an uptick in overall bike usage in each city, whether people were injured on bike-share bikes or their own, or even whether other types of injuries declined so much that brain injuries only seem more common. But the data supports the idea that bike-share users, who have to bring their own helmets or risk their noggins, might not be protecting themselves as best they can.
In spite of this, starting bike shares has helped a number of cities get a handle on the health and wellness of their populations. In Montreal, researchers found that not only did people's commute times decrease about 20 percent when they switched to bikes, but also that men saw decreased heart disease while women became less depressed overall. Additionally, bike-share users had lower injury rates than cyclists in general, likely due to eye-catching infrastructure such as bike paths and lights and the use of bigger, heavier bicycles.