The majority of college students now are 22 or older and the college population is becoming increasingly female, the Census Bureau reported yesterday.

The agency's report, "School Enrollment -- Social and Economic Characteristics of Students," surveyed school enrollments for 1980 and 1981.

The shifts in education it reflects are posing new and difficult choices for policymakers. For example, at a time when officials are debating the proper focus of college student aid programs, the survey found that 52 percent of college students are now 22 or older, defying the traditional notion that a college student is a young person who is still able to rely on parents for support.

Students aged 18 and 19 represented 25 percent of the total number of college students, according to the report, down from 31.6 percent in 1970.

Meanwhile, the proportion of students aged 25 to 29 increased from 11.4 percent in 1970 to 14.2 percent in 1981. The proportion of students aged 30 to 34 nearly doubled between 1970 and 1981, jumping from 5 percent to 9.9 percent.

Education Secretary William J. Bennett, defending his controversial proposals to cut college student aid, has argued that families could make up much of the difference by belt tightening and better financial planning.

More recently, C. Emily Feistritzer of the National Center for Education Information, sparked an emotional debate in the education community when she wrote in a column for The Washington Post last month that older students have been hogging student aid intended for the 18- to 22-year-olds.

Her column sparked some angry responses from older students who contended they are not in a better position to pay the high cost of a college education.

According to the Census report, much of the growth in the older student population can be attributed to women. Women students in the older age groups more than doubled their numbers between 1970 and 1981.

"You just can't look at higher education in the same old way," said Allan W. Ostar, president of the American Association of State Colleges and Universities. He said the shifting student population is changing the way professors teach, since older students who work tend to be more demanding and prefer evening classes.

"In the urban institutions in our association, the average age is about 28," Ostar said. "We've got more students going to classes after 4 p.m. than before 4 p.m. . . . . Those so-called 'traditional' 18-year-olds have been replaced by older students."