Researchers say they've developed a checklist of the subtle changes in a person's behavior that could turn out to be a signal of the early stages of Alzheimer's Disease.

"People often think (Alzheimer's) is all about memory loss," said Dr. Zahinoor Ismail, of the University of Calgary's Hotchkiss Brain Institute, in Canada.  "But it's not."

Researchers have previously focused on "mild cognitive impairment" - problems with memory and thinking - as an early warning sign of Alzheimer's disease.  But there's a growing recognition of "mild behavioral impairment" that could be even more telling.

These persistent changes in an elderly person's behavior could be exhibited with difficulties such as social withdrawal, angry outbursts, anxiety and obsessiveness.  But the key word is "persistent".

"We're not talking about a blip in someone's behavior," said Dr. Ismail.  "It's a sustained change from their former ways of functioning."  He adds that "out-of-character behavior can be the first sign of something going wrong in the brain". 

The checklist breaks symptoms of mild behavioral impairment into five groups:  "Decreased motivation" refers to apathy, or lack of interest, in the things a person once enjoyed, such as an interest in the lives of a patient's grandchildren.  "Emotional Symptoms" covers depression, anxiety, and irritability.

The third item on the checklist is a noticeable decline in a person's social graces, or a declining level of empathy for others.  Another warning sign of Alzheimer's is a change in "impulse control", especially when it comes to habits like drinking or gambling, or agitation or obsessiveness. 

The last is issues with perception or thought "content" - manifested by someone suffering from delusions or hallucinations.

Dr. Ismail says older adults may have mild behavioral impairment if they have any of those symptoms, at least periodically, for six months or more.

Keith Fargo of the US Alzheimer's Association welcomes the checklist, and hopes to see it confirmed through clinical testing.