The death March 18 of actress Natasha Richardson, two days after she fell during a beginner's lesson at Mont Tremblant, will inevitably fuel the controversy over helmets.

Ms. Richardson was not wearing a helmet. An autopsy found she died from bleeding in her skull caused by the fall she took on the ski slope.

The question arises with renewed vigor: "Do helmets reduce head and neck injuries in skiers and riders?"

The debate is nothing new. In 1997 the American Medical Association presented "Helmets for Recreational Skiing and Other Winter Sports in Children and Adolescents" to the Council on Scientific Affairs. Two years later, the U.S. Consumer Product Safety Commission released their conclusions, "Skiing Helmets - An Evaluation of the Potential to Reduce Head Injury."

Researchers collected data for the AMA study over a 15-year period on all types of skiing injuries at Sugarbush Ski Resort in Vermont, qualifying them by type, severity and age of the rider. At the end of the study, they tallied 11,795 injuries - 2.6 percent "potentially serious head injury" that resulted in skull fractures, concussions, severe brain injuries and death - approximately 0.07 per 1,000 skier days.

Researchers on the Consumer Product Safety Commission study found that of 17,500 total head injuries sustained in 1997, 7,700 could have been prevented or reduced in severity by wearing ski helmets, based on an analysis of the injuries by medical personnel who treated them.

More recent studies indicate that although the total number of injuries is declining, serious head injuries are on the rise due to the increased popularity of the sport and changes in equipment, like shaped skis that encourage skiing at higher speeds. The rise of terrain parks and glade skiing also are factors.

Head injuries are generally classified according to three types of blows: flat (from contact with snow or ice); hemisphere (from trees and lift towers), and edge (from sharp objects like sticks or rocks). The level of protection by the helmet has to do with two other factors: the speed of impact and the ability of the helmet to deflect the blow. Studies show that helmets protect the wearer at speeds less than 12 to 17 mph. Intermediate and expert skiers and riders average over 30 mph. Compounding the problem is the lack of helmet certification standards. Unlike motorcycle helmets that must meet stringent testing standards like Snell Certification, winter sports helmets are often designed with fashion in mind and are not required to meet any standards.

According to a 2007-08 demographic study conducted by the National Ski Areas Association, 43 percent of skiers and snowboarders elect to wear helmets while on the mountain. Use is highest among children under 9, with 70 percent of them put into helmets by parents or ski schools that require them for lessons. Helmet use is at 32 percent among young adults between 18 and 22. Helmet use also follows ability level: 26 percent of beginners wear them, while 55 percent of their advanced counterparts opt to wear lids.

The big question: Should skiers and riders wear helmets? It's a good one. Those against their use see little compelling evidence that wearing helmets saves lives or even reduces risk of serious head and neck injuries. Helmets certainly will not protect the wearer from ill-advised jumps or crashing into trees or lift towers. Those who favor their use say wearing a helmet at least reduces the severity of head injuries, and makes a difference in falls on beginner trails or collisions with other skiers or riders. They say that even a slight risk reduction could mean the difference between serious consequences and living to ski another day, so why not wear them?

The answer remains a personal one.