BOSTON (AP) _ U.S. doctors cut back their use of donated blood for transfusions during the 1980s, apparently because of fear of passing on AIDS, according to a study released today.

The study found that transfusions of whole blood and red cells totaled 9.9 million pints in 1980, reached a peak of 12.2 million pints in 1986 and have declined since then. During the same period, people have sharply increased the practice of setting aside their own blood for use during operations.

The study, directed by Dr. Douglas M. Surgenor of the Center for Blood Research in Boston, was based on a survey of about 5,800 hospitals and blood centers. It was published in today's issue of the New England Journal of Medicine.

Among the findings:

-Transfusions of whole blood and red cells fell to 11.6 million pints in 1987 and continued to decline in 1988, the last year of the survey.

-Transfusions of blood plasma dropped almost 9 percent during the decade.

-Donations of autologous blood - the practice of setting aside blood for one's own use - increased from 30,000 pints in 1982 to 397,000 pints in 1987.

-The supply of blood donated for others was unchanged between 1986 and 1988.

The researchers attributed the changes to fear of passing on the AIDS virus through transfusions. The chance of catching the disease from a transfusion has been slight since blood banks began screening for the virus in 1985.