People who report memory slips could be at risk of developing dementia down the road, even if they show no clinical signs of the disease, the American Academy of Neurology reported.

Dementia is characterized by severe impairment in functions such as: communication, ability to focus, reasoning and judgment, visual perception, the Alzheimer's Association reported.

"What's notable about our study is the time it took for this transition to dementia or clinical impairment to occur - about 12 years for dementia and nine years for clinical impairment - after the memory complaints began," said study author Richard J. Kryscio, PhD, of the University of Kentucky in Lexington. "These findings suggest that there may be a window for intervention before a diagnosable problem shows up."

To make their findings, researchers looked at 531 people who were of an average age of 73 and did not have clinical signs of dementia. The participants were asked annually if they noticed any memory changes, and were given a yearly thinking test over the course of about a decade, according to the American Academy of Neurology. After they died, 243 of the participants' brains were examined for evidence of Alzheimer's disease.

"Our study adds strong evidence to the idea that memory complaints are common among older adults and are sometimes indicators of future memory and thinking problems. Doctors should not minimize these complaints and should take them seriously," Kryscio said. "However, memory complaints are not a cause for immediate alarm since impairment could be many years away. And, unfortunately, we do not yet have preventive therapies for Alzheimer's disease and other illnesses that cause memory problems."

The study was supported by the National Institute of Health, the National Institute on Aging and the National Center for Advancing Translational Sciences. It was published Sept. 24, 2014 in the online issue of the journal Neurology®.