States with laws requiring all motorcycle riders to use helmets have far fewer deaths from head injuries suffered in crashes than those that do not, researchers said.

An analysis of motorcyclists' deaths in the United States from 1979 to 1986 found the death rate associated with head injuries was more than twice as high in states without helmet laws, Dr. Daniel Sosin of the federal Centers for Disease Control in Atlanta said Tuesday.Moreover, the 15,194 motorcycle deaths from head injuries during this period reflects "only a fraction of the head injury problem caused by motorcycles," Sosin and colleagues reported in the Journal of the American Medical Association.

A failure to use helmets not only leads to more deaths but also to more severe non-fatal injuries, the study found.

In 1986, 19 states and the District of Columbia had laws requiring helmet use by motorcycle drivers and passengers of all ages, the researchers said. Another 22 states had "partial laws" that required helmets for riders under the age of 21. Nine states did not require helmets: California, Colorado, Connecticut, Illinois, Iowa, Maine, Nebraska, Rhode Island and Washington.

The researchers found the annual death rate from head injuries among motorcyclists was 5.5 per 1 million people in states that require helmets, compared to 10.2 per 1 million in states with partial laws and 11.4 per 1 million in states with no laws.

Based on motorcycle registration, the death rate from head injuries was 3 per 10,000 motorcycles in states with full helmet laws, 3.7 in states with partial laws and 3.5 in states with no laws, the researchers said.