The folks who know the most about preventive health care aren't sharing enough of their knowledge with the people who need it most - their patients.

Doctors are not discussing information about safe sex, diet, exercise, seat-belt use and the perils of smoking and drinking as much as they should, according to a study appearing in Wednesday's Journal of the American Medical Association."A lot of physicians think patients don't want to hear it," said Deborah Taira, who conducted the research for the Health Institute at the New England Medical Center in Boston. "But even if the patients are grumbling, it doesn't mean doctors aren't having a positive impact" after giving advice.

The study also found that the advice doctors give varies depending on the income level of the patient, even though unhealthy behaviors are common among all income groups.

Taira drew her conclusions after surveying 6,549 Massachusetts state employees in 12 health plans. Participants were asked to describe their health habits and whether their regular physician ever talked to them about risk behaviors. The patients then indicated whether they changed their behaviors as a result of those discussions.

The research found that physician discussion of health-risk behaviors fell far short of the universal standards recommended by the U.S. Preventive Services Task Force, a government-appointed panel that establishes guidelines for preventive practices.

The study also showed that frequency of doctor advice on risky behaviors varied widely by topic. For example, 70 percent of doctors of obese patients discussed diet with them. Nineteen percent of doctors of unmarried patients talked about safe sex practices. And 39 percent of doctors whose patients said they consumed more than 13 alcoholic drinks per week, discussed the dangers of drinking too much.

Studies show that about 40 percent of all deaths are attributable to behaviors such as smoking, over-eating, lack of exercise, alcoholism and not wearing seat belts. The estimated annual cost to society of cigarette and alcohol consumption alone is $179 billion, according to one study.