More than 5.2 million square feet of new office space was leased last year in the Washington area, according to a report from Julien J. Studley Inc.

In the District, according to Studley, nearly 1.9 million square feet of space was leased -- almost double the total for 1979. Studley reported leasing in suburban Maryland at 1.6 million square feet, an increase of 50 percent. Northern Virginia leasing, which has encountered some overbuilding of office space in recent months, leased 1.7 million square feet in 1980. Much of the space was preleased in buildings that have yet to be completed.

The Studley report showed that only Houston, where 9.3 million square feet of office space were leased last year, exceeded the Washington area total. Los Angeles was third in office leasing with 4.7 million square feet; greater Chicago fourth with 3.5 million square feet; and New York City fifth with 2.6 million square feet.

Another national survey, by the Coldwell Banker realty firm, showed that the index of vacant space in major cities increased to 4 percent in December from 3.9 percent in September. However, the downtown Washington vacancy index remained at 0.3 percent, one of the lowest figures in the nation. Only the 0.2 percent vacancy rate in Los Angeles is lower.

Additionally, the Building Owners and Managers Association, based here, reported that office space occupancy across the nation declined in the second half of 1980 to 92 1/2 percent from 94 percent earlier in the year. The BOMA report, based on answers from members, showed that both the Washington and New York City areas had gains in occupancy. For Washington the occupancy figure was 99 percent.

Elsewhere on the area office and leasing front, Arthur Rubloff & Co. reported that the Richmond, Fredericksburg & Potomac Railroad Co. leased approximately three acres on N. Henry St. in Alexandria to Federal Express, a domestic overnight delivery service. Federal Express is building a 34,000-square-foot central distribution station on the site.

In North Bethesda, the Rock-Wall II building, located opposite the White Flint Mall, is now ready for leasing. Danac Associates said that 185,000 square feet is available in the building developed by Equitable Life Assurance Society of the U.S.