New research shows that in a crash, car or automobile air bags may increase the risk of serious injury for short or tall front-seat passengers.
The study by Craig Newgard, of Oregon Health & Science University, is due presentation at the annual meeting of the Society for Academic Emergency Medicine, in Chicago, this week.
Newgard based his results on an analysis of injury statistics for the period 1995-2005, from a motor vehicle crash database.
The database shows that during the years studied, 52,552 drivers and 14,732 passengers were involved in crashes.
Most of those people were not seriously injured, but 2.5% of the drivers and 2.6 percent of the passengers sustained serious injuries to any part of the body.
Newgard reviewed data on the drivers' and passengers' height and weight, air bags, and 10 factors about the crash.
Significant findings were that air bags were "modestly protective" for front-seat passengers of medium height, - between 5 foot 3 inches tall to 5 foot 11 inches tall.
However, it was seen that "air bags appear to increase the risk of injury for large- and small-stature adults."
In addition, Newgard calculated that for drivers taller than 6 foot 3 inches, air bags were associated with a 5 percent greater risk of serious injury. He also estimated that for drivers shorter than 4 foot 11 inches, air bags were associated with a 4 percent increase in the risk of serious injury.
Weight was not observed to affect the results, Newgard noted.
Yet, Newgard's study does not provide information on how far the drivers and passengers were seated from the air bags in the crashes.
Distance from the air bag is the most important factor in preventing air bag injuries, according to the web site of the National Highway Transportation Safety Administration (NHTSA).
"There is no precise height and weight at which an individual is considered to be at risk" from air bags, says the NHTSA. "The primary determinant as to whether an individual will be injured by a deploying air bag is the distance from which the individual is seated from the air bag."
The NHTSA notes that there is also no precise distance guaranteed to avoid air bag injury since all air bags are unique and deploy with different forces.
The NHTSA's advice included the following:
* Wear your seatbelt.
* Sit as far from the air bag as possible to allow the air bag to deploy.
* Short drivers should move the driver's seat back and tilt the seat back slightly to allow space between the driver's chest and the steering wheel.
* Drivers should refrain from leaning forward.
* to the extent possible, drivers should hold steering wheels from the side, so that their arms aren't in the way of the air bag.
Says Newgard: "There's been a lot of interest in airbags for the last 10 to 15 years.
"Airbags are designed to be a protective mechanism for automobiles but as the years have gone on and we've gained more insight we know that certain groups of people are at risk of injury rather than have a benefit from them."
"That's pretty well established in kids and there have been some small case reports to suggest that maybe small stature adults are also at risk but it's never really been demonstrated conclusively," Newgards adds.
Yet, Newgard says, "From the study, both small-stature and large-stature occupants look to be at increased risk of injury from the airbag rather than having a benefit."