A paper released earlier this month found cyclists who ride without a helmet are more likely to take risks. It’s generating a lot of talk.

The Conversation did its own investigation and ran the story under the heading “Crash data shows cyclists with no helmets more likely to ride drunk“. The Sydney Morning Herald took a more sober approach — it reported “Cyclists without helmets ‘likely to be risk-takers’“.

Risky behaviour is one of the issues addressed in the paper, but these reports distracted attention from a couple of other important results. The key purpose of the research reported in the paper was to examine the effectiveness of helmets in minimising head injuries in the event of a collision between a bicycle and a motor vehicle.

The paper documents an investigation undertaken by four UNSW researchers in the April 2013 edition of Accident Prevention and Analysis, a leading journal in this area. They examined 6475 collisions between cyclists and motor vehicles in New South Wales where the accident was reported to police, hospital data was available if applicable and the helmet-wearing status of the cyclist was recorded.

The authors were able to combine rich information about the type and severity of injuries with data about the circumstances of the accident.

Their headline finding is that helmets confer a large protective effect in the event of a collision with a motor vehicle. The odds of sustaining a “moderate” head injury in a collision are 1.9 times greater if the cyclist doesn’t wear a helmet. However, the odds of suffering a head injury classified as ‘serious” are 2.6 times greater if the rider’s unhelmeted. In the case of a “severe” head injury they’re 3.9 times greater.

When the researchers broke head injuries down by type, the estimated odds of suffering a “serious” or “severe” skull fracture if no helmet is worn is 4.6 times greater.

These findings go against the meme that helmets only offer protection in the event of a minor accident, like simply falling off a stationary bike or while pedalling at low speed. They contradict the myth that a helmet is useless in an accident with a car. The authors say the research shows the benefit from wearing a helmet increases with the severity of the injury.

It’s also very likely the better odds offered by helmets are understated. That’s because the number of riders who were involved in a collision with a motor vehicle but avoided a head injury because they wore a helmet can’t be known.

And there’s comfort in the finding that more than 90% of cyclists who were in a collision with a car didn’t sustain a head injury. Those that did, however, were more likely to have collided with a larger vehicle; or to be cycling on a road with higher maximum speeds; or to have disobeyed a traffic signal; or to not be wearing a helmet.

Worryingly, the researchers also found children who were involved in a collision were much more likely to be unhelmeted. Children aged 12 years or less comprised 19% of all those who weren’t wearing a helmet at the time of their accident but just 7% of those who were.