Aging cats who forget their owners, cry out in the night and become confused may be suffering from Alzheimer's disease. New research shows felines can suffer the same memory-robbing illness that causes dementia in humans.

U.K. and U.S. scientists have identified a protein accumulating in the nerve cells of cats' brains causing mental deterioration, they said in a statement today. In humans with Alzheimer's, the same protein creates tangles inside nerve cells, inhibiting messages being processed by the brain.

A century after Alzheimer's was identified, researchers are still trying to find risk factors that cause the ailment, which afflicts 28 million people worldwide. Now that the disease has been found in cats, who don't live as long as humans, researchers may be better able to assess the effects of diet, high blood pressure and drugs on the course of the disease.

"Cats are exposed to the same environmental stresses and strains and toxins that we are," Danielle Gunn-Moore, a veterinarian at Scotland's University of Edinburgh who led the study, said in a telephone interview.

Gunn-Moore and her husband, an Alzheimer's disease researcher at Scotland's University of St. Andrews who assisted his wife in the study, are trying to use their findings to investigate new avenues for a cure.

The study "has given us an insight into the molecular changes that are occurring in the degenerating brain," Frank Gunn-Moore said in the statement. "From this knowledge we are now currently trying to develop new and novel treatments, which will be able to help both cats and humans."

LIVING OLDER

Alzheimer's is the most common cause of dementia in Western countries. A 10th of people older than 70 have significant memory loss, and in more than half the cause is Alzheimer's disease, according to Harrison's Principles of Internal Medicine. The annual cost for caring for a patient in an advanced stage of the disease is estimated at $50,000, it said.

The number of victims is expected to grow fourfold by the middle of the century as the population ages and baby boomers reach retirement, according to the Alzheimer's Association.

As with humans, the life expectancy of cats is increasing and with this longer life runs the greater chance of developing dementia. More than a quarter of pet cats aged 11 to 14 years develop at least one old-age related behavior problem and this increases to more than half for cats older than 15, Danielle Gunn- Moore said.

CRYING IN THE NIGHT

Gunn-Moore, who is one of six recognized feline specialists in Europe, began researching Alzheimer's when her own cat, Cardhu, developed dementia six years ago. Before he died earlier this year, the 14-year-old puss "had taken to living under the bed," she said. "As long as I crawled under the bed to cuddle him, he was a very happy boy."

That's a common sign in the advanced stage of the illness, Gunn-Moore said. Earlier symptoms may include crying in the night and loss of litter-box training.

"They get disoriented," she said. "I have seen some cats that are so severely senile that they shrink their world — they get so that they won't leave one corner of a room."

A diet rich in antioxidants, mental stimulation and companionship can help ward off Alzheimer's in cats, as it does in people, according to Gunn-Moore.

Scientists have yet to determine what triggers the disease. While numerous environmental factors, including aluminum, mercury and viruses, have been proposed as causes of Alzheimer's, none has been demonstrated to play a significant role, according to Harrison's, a medical text book.