Although the majority of its victims are under age 40, AIDS is increasingly striking another group of Americans: the elderly.

By 1992, according to a report in the Journal of Gerontology, an estimated 10,000 people over age 60 will have contracted the disease. Half are believed to have contracted the disease through blood transfusions, the other half mostly from homosexual intercourse.

"Treating elderly AIDS patients is more difficult," said Newton E. Kendig, a medical fellow at the National Institute of Aging. "Once they get infected, they develop the disease sooner, then die sooner," he said. In addition, he said, older patients frequently have adverse reactions to drugs prescribed for AIDS.

The human immunodeficiency virus that causes AIDS also induces dementia in approximately two thirds of its victims. Among the elderly, diagnosis is more complicated because Alzheimer's disease, Parkinson's disease and other ailments all can cause dementia. "Doctors may miss the fact that an elderly person has AIDS and misdiagnose the patient's dementia as another disease," he said.

Kendig and William H. Adler, the chief of the immunology section at the NIA, stated that the physical health of elderly AIDS patients deteriorates more rapidly than the health of younger patients. The researchers also warned that a family support system is often unavailable to elderly AIDS patients. According to Kendig, elderly patients feel isolated and excluded from support groups geared to those a generation or two younger. "They don't feel that they can tell anyone that they have AIDS," he said.

The researchers advocate more AIDS education for older people, as well as the formation of support groups that may draw elderly AIDS patients out of emotional isolation.