A growing number of medical experts are calling for laws across Canada to require adults, not just children, to wear helmets while riding bicycles.

Helmets that can prevent serious, life-long head injuries cost just a few dollars, but a severe brain injury can cost society $8 million after taking into account long-term medical costs, doctors say.

"A brain injury is permanent -- you just don't recover from a brain injury like you do a broken leg or broken arm," Dr. Charles Tator, president of ThinkFirst Foundation of Canada, told CTV News.

"We think of a brain injury as one of the worst, because there is so little we can do for the severe ones."

Those who have suffered severe head trauma often need medical attention 24 hours a day because they have no memory and can't perform simple tasks by themselves, Tator says.

New studies show that deaths from bike accidents have dropped by 52 per cent in regions where children must wear helmets.

Yet for adults, biking-related deaths continue unchanged and the number of head injuries is even rising in some regions.

"What was really surprising was the percentage of adults treated in Ontario emergency department with head injuries has gone up by about 20 per cent over the last three years," said Alison Macpherson, an assistant professor at York University's School of Kinesiology and Health Science.

One of the arguments against helmet laws is that it would repel people from cycling, but the number of cyclists went up after the helmet law was enacted in British Columbia, Macpherson said.

A 2004 study conducted after the introduction of a bicycle helmet law for children under the age of 18 in Alberta did not see an increase in use among adults.

"The introduction of helmet legislation restricted to youth in Alberta was associated with an increase in helmet use for this age group, but had little effect on adult riders, suggesting that adult legislation should be considered," said the authors of the study published in the journal Injury Prevention.

But there are less than a handful of Canadian jurisdictions -- including the provinces of Nova Scotia, New Brunswick, and British Columbia -- that require adults to wear helmets and some doctors say this should become the law across the country.

"Studies are showing that with legislation with rules and enforcement, people do wear helmets," Tator said.

• ThinkFirst's Give-A-Kid-A-Helmet Program

Michael Larkin learned the value of wearing a bicycle helmet the hard way.

He went for a quick ride around the block without a helmet when he suddenly went airborne and landed in the middle of the road.

"Seven broken ribs, a broken scapula in two places, punctured lung, collapsed lung, fractured skull," he listed.

"If I had been wearing a helmet I wouldn't have spent five months in rehab," he said.

With a report from CTV medical reporter Avis Favaro and producer Elizabeth St. Philip