TORONTO (Canadian Press) -- New guidelines suggest that some of Miss Daisy's peers may still safely take to the roads -- though they need to start thinking about life after driving.

The American Academy of Neurology issued updated guidance for neurologists Monday, dropping a previous, contentious blanket recommendation that people with mild dementia should not drive.

The lead author of the new guidance, Dr. Donald Iverson, said studies that have been published since the earlier recommendation was issued show that about three-quarters of drivers with mild dementia can still pass driving tests and can drive safely.

He said the group felt it should issue guidance that helps doctors identify those patients who should stop driving without restricting those who can still drive. But at the end of the day, decisions need to be made on a case-by-case basis.

"It's a guideline with the emphasis on the guideline. It's not a prescription for what to do or what not to do. It's for clinicians to incorporate into their judgment and experience and use in counselling patients," said Iverson of the guideline, which was published in the journal Neurology.

The publication coincided with a presentation on the topic at the organization's annual scientific meeting currently underway in Toronto.

Iverson, who led the review of more than 6,000 studies on the issue, said figuring out when people in cognitive decline should stop driving is "a really difficult issue."

"The world isn't black and white and there's no boundary where all of a sudden you go from competence to incompetence. There's a grey area there and there's a transition," he said in an interview.

Where the previous guidance said doctors should tell patients newly diagnosed with mild dementia not to drive, the new recommendation suggests doctors should have a discussion with the patient and family members about the fact that the patient's driving days are numbered. The conversation should direct the parties to start thinking about how the patient will get around once he or she has to stop driving.

The guidance suggests caregivers should trust their instincts. Studies have shown that when caregivers think an older relative's driving is becoming unsafe, they are generally right.

"If you have a concern, then I would say trust your instincts, report it to the doctor and those instincts are probably validated," said Iverson, a neurologist in private practice in Eureka, Calif.

The guideline lists warning signs that might signal a person with mild dementia is hitting the point where it is unsafe to drive.

People who are driving less or avoiding driving in certain conditions -- such as at night or in the rain -- may be having cognition related problems. That is also true of drivers who start having collisions or amassing motor vehicle violations or who start to demonstrate aggressive or impulsive personality traits.

The guidance also states that the patient's own assessment of his or her driving skills is not useful when trying to determine whether it is still safe for a person with mild dementia to drive.

Copyright The Canadian Press, 2010