BOSTON - A national rise in public bike sharing programs could mean less air pollution and more exercise, an environmental and health win-win for people in the cities that host them, but according to researchers at Beth Israel Deaconess Medical Center, more than 80 percent of bike share riders are putting themselves at significant health risk by not wearing helmets.
"Head injury accounts for about a third of all bicycle injuries and about three-quarters of bicycle related deaths, so these are some pretty shocking numbers," says lead author and emergency medicine physician Christopher Fischer, MD.
The results of the study are published in the April 30 online edition of the Annals of Emergency Medicine.
Bike sharing programs where riders rent bicycles from kiosks located throughout a metropolitan area have become popular in European cities like Paris and Barcelona. There are 15 bike sharing programs in operation in the United States and 30 more under development.
The study examined the Capital Bike share program that began in the Washington, DC area in September, 2010 and Boston's Hubway bike share program launched in July, 2011 with 61 kiosk locations and 600 bikes.
Fischer and team used trained observers to collect data on adult cyclist helmet usage in Boston and Washington over 43 observation periods totaling more than 50 hours. The sites were located near bike rental kiosks but all bikers, whether they rented bikes or rode their own, were recorded. More than 3,000 bicyclists were observed.
"We were surprised to find that of all bicyclists, more than half rode without helmets," says Fischer. "But it was even more concerning to learn that four out of five bike share riders were out there without helmets."
Studies show that "helmet use is associated with decreased rates of head injury and mortality in riders of all ages, with bicycle helmets decreasing the risk of head and brain injury by 65 to 88 percent," write the authors.
While helmet wearing is encouraged in the Boston and Washington, DC bike sharing programs - and websites offer locations where renters can purchase helmets - helmet use is not a requirement for bike rental.
"Bike sharing programs have the potential to offer a lot of benefits to cyclists and cities, but it's important to encourage safe cycling," says Fischer. "We know that wearing a helmet reduces the risk of head injury dramatically and we believe that helmets should be more readily available at bike rental sites."
Other study authors include Czarina E. Sanchez, MD, Kathryn A. Volz, MD, Leon D. Sanchez, MD, MPH and Shiva Gautam, PhD from Beth Israel Deaconess Medical Center and Mark Pittman, MD and David Milzman, MD from Washington Hospital Center in Washington DC, and Han Huang, MS from Georgetown University School of Medicine.
Beth Israel Deaconess Medical Center is a patient care, teaching and research affiliate of Harvard Medical School, and currently
ranks third in National Institutes of Health funding among independent hospitals nationwide. BIDMC is clinically affiliated with the Joslin Diabetes Center and is a research partner of Dana-Farber/Harvard Cancer Center. BIDMC is the official hospital of the Boston Red Sox. For more information, visit