At the rate he is going, Jason has 30.1 years to live. He is 39 years old, but his "health age" is 42.2 years.

If he follows specific health practices (cutting cholesterol, exercising, drinking less and lowering his blood pressure) he can achieve the fitness level of a 32.1-year-old and increase his life expectancy by 9.2 years. Instead of dying at 69.1, he could live to be 78.3.

Jason received these "life-expectancy predictions," plus a list of the likely causes of his death and suggestions for things he can do to live longer as part of a Health Risk Index performed by the Ohio-based Medical Datamation.

Using the latest computer technology and medical statistics, a handful of companies across the country are offering similar services. Called Health Hazard Appraisals, they are designed to help people recognize their major health risks and adopt healthier living habits.

An individual fills out a questionnaire that examines physical measurements such as blood pressure, height and weight; life-style factors such as smoking, exercising and driving habits, plus personal and family histories of disease.

By measuring these figures against national averages for persons with similar physical characteristics, the computer comes back with a sometimes-shocking profile of that individual's disease-and-death risks, coping skills and mental health.

"It's like a mirror," says Dr. James Bernstein, president of General Health, a Georgetown firm that markets a personal health profile. "It reflects accurate, individualized information about a person and gives people the competence to manage their own health.

"It's not fortune-telling. It's a probability statement that answers 'How do I compare with the average group like me?'"

The health hazard appraisal was developed in the early 1960s by Drs. Lewis C. Robbins and Jack Hall at the Methodist Hospital of Indianapolis, Ind. It grew out of a 20-year study of the health and life styles of 5,000 residents of Framingham, Mass.

"We were trying to see who dies of what disease and find the relationships between life styles and cause of death," says Dr. Robbins, formerly chief of the Cancer Program for the U.S. Public Health Service.

"Suddenly it made sense that this would be the way medicine would go in the future. We could pick the characteristics that put you at high risk, and then apply the best prevention."

A new branch of medicine has grown out of the study of health hazards. Called prospective medicine, it uses health-hazard appraisals as a patient-education tool and works to reduce people's exposure to known health risks.

"The word prospective means being able to see in the future," explains Scott Sheedy, director of prospective medicine for the Methodist Hospital and a member of the Society of Prospective Medicine.

"Every disease has a natural history, and the earlier the intervention the better. We believe 50 percent of the diseases a doctor sees in an office are preventable or delayable."

The health-hazard appraisal is only a teaching aid, Sheedy stresses. "People do not instantaneously change lifelong habits. We hope it's enough to motivate them to modify their behavior."

The advantage of using this kind of teaching tool, he says, is that it illustrates graphically exactly how each habit affects that inidvidual's health -- complete with a person's projected "expiration date."

"It's like a TV game show -- 'You Bet Your Life,'" Sheedy says."By seeing the statistics and probability of your death from certain habits, you realize you are betting your life when you indulge in certain things.

"Although everybody knows it's harmful to smoke or drive while drunk they take the attitude that lung cancer or a car accident won't happen to them. But when you work out the probability of it actually happening, they can really see the hazard in perspective.

"And it's more effective than a fat, cigarette-smoking physician telling you to stop smoking and lose weight."

Last year the Methodist Hospital began offering health-hazard appraisals as a fringe benefit to employes.

"The hospital is concerned about the health of people who work here," Sheedy says. "Also it's selfish -- turnover, sick leave and absenteeism are expensive."

Several federal health agenies are providing grants for study of the appraisals, and some large businesses, including Ford Motor Company, have used them for executives.

Although physicians' acceptance of the computerized profiles has been slow, several medical schools now teach prospective medicine and the concept is growing, says General Health's Bernstein.

"We're creating a product and service that can help people improve their health," says Dr. Bernstein, who left surgery and cancer research because he was frustrated with working to heal diseases that might have been prevented in the first place.

"It's assumed that the person can do things -- like make decisions what to eat or not to smoke -- to move in the direction of health. It's a nontraditional way of thinking. Doctors practice medicine, but people practice health."