NEW YORK (AP) _ People over age 60 who decide to kill themselves keep the decision secret and usually get the job done on the first try, participants at a conference said Thursday.

''There's a huge generational gap in the attitude about suicide,'' Robert Schussel, a Blue Cross marketing researcher, said at a forum on a new Gallup survey about attitudes about suicide.

''Teen-agers talk about it a lot, there are a lot of attempts, often not successful,'' he said.

But for older Americans, ''Suicide is really a taboo subject. They don't talk about it, they don't talk to their friends about it, they just go out and do it,'' Schussel said.

In the survey of 802 Americans age 60 and over, only 1 percent said they had thought about committing suicide within the last six months.

One reason few older people talk about committing suicide is the fear that such talk will land them in a nursing home, said Esther Dyer, an executive of Empire Blue Cross and Blue Shield medical insurance.

The elderly, however, have the highest rate if suicide of any age group in the nation, and the numbers are drastically underreported, said Nancy Osgood, a Virginia Medical College professor specializing in the ills of the aged.

Osgood said many suicidal old people take a slow, indirect way out by starving themselves or not taking necessary medicine.

National statistics show older people, 26 percent of the U.S. population, commit 39 percent of the officially recognized suicides. Their rate, 20.1 suicides per 100,000 people, is 65 percent higher than the nation as a whole, Dyer said.

The rate also is nearly twice that of Americans at the other end of the age scale, said George Gallup Jr.

Among older Americans, Gallup said, people who kill themselves tend to be less religious than their contemporaries, are not likely to reveal their intentions and have not tried to get help.

Other factors include lack of a social life, low income and poor health, Gallup said.

Gallup said the survey, conducted by telephone last month, couldn't be generalized for all eldery Americans. Aged people who are institutionalized or unable or unwilling to answer a phone were underrepresented, he said.

A typical old-age suicide is a white man who lives alone in one of the mountain states and uses a gun to kill himself, Dyer said.

Women, who keep up their social contacts in old age, account for only 20 percent of post-age 65 suicides and usually use drug overdoses or poison.

David Clark of the psychiatry department of Rush-Presbyterian-St. Luke's Medical Center in Chicago said unrecognized psychiatric illness - not living conditions - is the major contributor to old-age suicide.

Dr. Yeates Conwell of the University of Rochester Medical Center agreed. He said 90 percent of suicides of all ages had ''diagnosable psychiatric illness.''

''Of all factors we know, it is one of the most consistent and pervasive,'' he said. In the old, that is likely to mean depression, ''an illness for which there is treatment and whose prognosis is good.''