Just How Effective Are Helmets?

Last year, the Washington Area Bicyclist Association (WABA) petitioned the government to withdraw its claim that bicycle helmets reduce the risk of head injury by 85%. They prevailed, and both the Center for Disease Control (CDC) and the National Highway Traffic Safety Administration (NHTSA) removed the fact from their websites. What was the reasoning behind WABA’s actions? According to an article posted on the organization’s website, spreading bad information can be detrimental, even when the intentions are good.

A study carried out in 1989 is responsible for the information in question. A team of investigators led by Dr. Robert S. Thompson collected data pertaining to cyclists who were being seen in Seattle area hospitals after having crashed. Of the cyclists being treated for head injuries, only 7% reported wearing a helmet. This is in contrast to 24% of cyclists who didn’t suffer head injuries. From this, researchers estimated that the occurrence of head injury was reduced by 85% simply by strapping on a helmet.

The problem with this study is two-fold. First, it’s a case-control study, meaning that it relies on observing and collecting data rather than on trials and experimentation. This type of study is good for proving an effect, but is less effective for quantitating that effect. Second, the study’s findings were not reproducible, though dozens of attempts were made. Researchers found that helmets could, indeed, reduce the risk of head injury, but the amount by which the risk was reduced varied and never quite reached 85%.

There’s no doubt that wearing a bicycle helmet can save your life. Helmets protect your head by forming a cushion. They can significantly reduce the chance of skull fractures because they distribute the force of an impact. So why force a retraction of data that communicates the effectiveness of bike helmets, even if it’s not quite correct?

Helmets today are designed with comfort and performance in mind. They are aerodynamic and lightweight, with ventilation holes and a softer shell. They are also, according to some, not as safe as they once were.

This, WABA cautions, is what comes from relying on bad data. Because 85% is such a reassuring figure, riders have become complacent and have ceased to push for better helmets. Thus, the focus has shifted toward aesthetics and away from safety.

All of this is not to say that helmets are ineffective. Helmets are absolutely essential for safety. Their effectiveness, however, has been overstated, and it’s important to be aware of this. When we stop relying on misinformation, we can start looking at ways to improve safety regulations and standards, and make bicycle helmets even more effective than they already are.