If your mother or father had died young of a heart attack, don't you think you would take better care of yourself? Not necessarily, say researchers at the University of Michigan Fitness Research Center.

Such individuals take some of the easy steps thought to prevent heart attacks, the researchers found, such as getting their cholesterol level checked, but they usually shy away from the life style changes that require some real effort, like exercising.

Louis Yen, a Michigan graduate student, and Dr. D.W. Edington compared the habits of 1,270 persons whose parents had died of a heart attack before age 60 to those of 14,679 in a control group.

Persons in the high-risk group, they found, were significantly more likely than others to engage in health behaviors associated with coronary heart disease: smoking, using drugs and failing to exercise.

According to Yen and Edington, those with fatal heart attacks in their families also were less careful with their health in ways not related to heart disease. They tended to get less sleep than the controls, more often failed to use seat belts and were involved in more violent arguments.

The only arena in which high-risk individuals took steps toward prevention was in their use of the medical care system. They were more likely than members of the control group to know their cholesterol levels and blood pressure readings and to get regular rectal and breast examinations. . . .