A drug used to treat narcotic overdoses shows promise for improving memory and mental performance of senile people, according to a New York University study to be released today.

But NYU's Dr. Barry Reisberg emphasized that the findings with the drug naloxone "are very preliminary."

"There needs to be far more investigation," he said. "We by no means have a treatment at this point."

Health and Human Services Secretary Margaret M. Heckler, in her first news conference, cited the government-sponsored research as one of several "promising results" in the investigation of senile dementia, a devastating old-age affliction known technically as Alzheimer's disease.

She announced formation of a HHS task force to "identify the most promising research avenues" and help translate "that research into policy, programs and practical means for improving the quality of life for older Americans."

Alzheimer's disease is the "fourth leading cause of death for the elderly, and its complications kill 100,000 people each year. It is the major reason that so many elderly people end up in nursing homes, at a cost of $6 billion a year," Heckler said.

Such high-level attention to senile dementia represents an unusual departure from the more traditional focus on chronic killers like heart disease and cancer, which have claimed the most attention and funding. Although many areas of research have suffered cutbacks, Heckler said Alzheimer's disease research has continued to climb under the Reagan administration from nearly $17 million in fiscal year 1981 to a proposed $25 million in 1984.

One government official noted that funding had been rising since the late-1970s, but "the field could clearly use a lot more money."

Studies are being conducted under the National Institute of Mental Health (NIMH), the National Institute on Aging and the National Institute of Neurological and Communicative Disorders and Stroke.

NIMH Director Dr. Herbert Pardes said the findings with naloxone, although "admittedly extremely early," were singled out because the drug is one of the first to show "clinical improvements with individuals in residential centers for the elderly who actually had a turnaround in functioning for the better."

NYU's Reisberg said that in a controlled study with seven patients, most showed at least "some response" after receiving naloxone, and in three "the clinical effects were of sufficient magnitude to be noted by family members."

He said improvements in thinking appeared to last from one to three weeks after an injection, and were maintained in one patient for about three months.

In the most dramatic case, Reisberg said, a 73-year-old woman with severe senility was able to perform simple mental tasks like counting backward and reciting her address, the current president or the weather outside, all of which she had trouble doing before.

How the drug might affect Alzheimer's disease is not known, but earlier research has shown that it can block the effects of natural opiates or painkillers in the brain.

Naloxone appears to have no serious side effects, Reisberg said, but it has not yet undergone long-term testing. He said it apparently is safer than the drug physostigmine, which also is being tested on Alzheimer's patients at two other New York centers. Reports on both drugs appear in letters published in today's New England Journal of Medicine.

Researchers are optimistic about eventually finding treatments for senile dementia, but they emphasize that no single drug is likely to be satisfactory for all patients.