New research suggests that older adults who will develop dementia may start to lose awareness of their memory problems two to three years before the actual onset of the disease, HealthDay reported.

Researchers at Rush University found that unawareness of one's memory problems could be an inevitable feature of late-life dementia, driven by a buildup of dementia-related changes in the brain

"Lack of awareness of memory loss is common in dementia, but we haven't known much about how common it is, when it develops or why some people seem more affected than others," researcher Robert S. Wilson said in a statement.  "Most studies of memory unawareness in dementia have focused on people who have already been diagnosed. In contrast, this new study began following older adults before they showed signs of dementia."

Researchers collected and analyzed data from more than 2,000 participants who participated in from three ongoing studies. In each study they tracked older adults for more than 10 years. At the beginning of the study, the participants were an average of 76 years old and showed no signs of memory or cognitive impairments, The Guardian reported.

Two hundred and thirty-nine people were diagnosed with dementia during the study. For them, memory awareness was stable and then began to drop sharply an average of 2.6 years before the onset of dementia. This followed several years of memory decline.

"Although there were individual differences in when the unawareness started and how fast it progressed, virtually everyone had a lack of awareness of their memory problems at some point in the disease," Wilson said.

Unexpectedly, memory unawareness began earlier in younger people than in older people. That may be because older people were more likely to expect memory loss as a normal part of aging, the researchers suggest.

"This study underscores the importance of family members looking for help from doctors and doctors getting information from friends or family when making decisions about whether a person has dementia, since people may be unable to give reliable reports about the history of their own memory and thinking abilities," Wilson added.

The findings are detailed in the journal Neurology.