ROCHESTER, Minn. — In terms of concussions, women’s ice hockey is the most dangerous N.C.A.A. sport.

Addressing the Mayo Clinic conference on concussions in hockey Tuesday afternoon, the University of North Carolina researcher Jason Mihalik outlined some of the theories surrounding the astonishingly high concussion rates in women’s hockey, a sport in which body checking is not allowed.

There is only very limited head impact data available for women’s hockey, Mihalik said. But that which is available (mainly from an analysis of 16 years of N.C.A.A. injury reports) is surprising.

The concussion rate in N.C.A.A. women’s ice hockey is 2.72 per 1,000 player hours. For men’s ice hockey it’s 1.47 per 1,000. Even for N.C.A.A. football, the rate is 2.34 per 1,000 — lower than it is for the women on the ice.

Concussions comprised about 25 percent of the injuries in women’s ice hockey, the highest cause of injury in the sport. In men’s ice hockey concussions account for 9 percent of the injuries (No. 2 in the sport), and in football they account for 7 percent (No. 3 in the sport).



How is it that a sport that does not allow body checking should have such a high concussion rate? Mihalik said the phenomenon was still under study, but it may have to do with women not anticipating a hit. Studies in men’s and boys’ hockey show that the greatest risk of concussion occurs in unanticipated hits — and in women’s hockey players may never anticipate a hit.

Mihalik also theorized that female players’ neck muscles tend to be less strong than those of male players, which may in turn allow the head and brain to be whipped around more in a collision. But, he cautioned, preliminary data show that neck strength is far less of a factor in concussions than whether a player anticipated a hit.

“Unanticipated collisions tend to cause concussions,” Mihalik said.

Doug Stacey, the chief physiotherapist for of Canada’s national women’s teams, including the 2010 gold medal-winning Olympic team, also theorizes that neck strength is the main determinant why women’s concussion rates are so much higher. (Women, he pointed out, have 43 percent less head/neck mass.)

Stacey was skeptical of the idea that women tend to honestly report concussions while men tend to underreport. “From my experience that’s a stereotype,” he said. “I have players who will look at me straight in the eye and say they’re fine when they are in fact experiencing symptoms.”

He cited the concussion stats for the Canadian women’s team in 2009-10: nine concussions among eight different players. In three, the symptoms lasted longer than 21 days.

In general, Stacey pointed out, women experience greater symptoms from concussions; greater cognitive impairments; and have greater mortality and morbidity rates associated with brain trauma.