Declining awareness of memory loss precedes dementia

New research indicates that people who go on to develop dementia can start losing awareness of their memory problems up to 3 years before the condition arises.

The study authors report that awareness of memory impairment typically begins to decline around 2-3 years before the onset of dementia.

These latest findings suggest that unawareness of one's memory problems is an inevitable feature of late-life dementia, driven by a buildup of dementia-related changes in the brain.

The study, published in Neurology, also identifies that a number of changes in the brain related to dementia are associated with a decline in memory awareness.

Dementia is a collective term to describe a group of symptoms severely affecting cognitive functioning. The most common form of dementia is Alzheimer's disease; according to the Alzheimer's Association, Alzheimer's disease is the sixth leading cause of death in the US, with 5.3 million Americans of all ages estimated to have the condition.

Although declining awareness of memory loss is common among people with dementia, experts do not know much about how prevalent it is, when it develops or why it affects some people more than others.

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.

The study analyzed 2,092 participants from three longitudinal studies who reported no memory or cognitive impairment at the beginning of the study. The participants were subjected to testing each year for more than 10 years to evaluate their memory and thinking capabilities. Participants had an average age of 76 at study baseline.

'Virtually everyone had a lack of awareness of their memory problems'

A total of 239 participants were diagnosed with dementia during the study follow-up period. For each of these participants, memory awareness was stable to begin with. However, the researchers observed that memory awareness dropped sharply an average of 2.6 years prior to the onset of dementia. After this point, several years of memory decline occurred.

Fast facts about dementia

• Typical symptoms of dementia include memory loss, disorientation and poor judgment
• Memory loss alone does not indicate dementia, as there is a certain extent of memory loss that is a natural aspect of aging
• Nearly two thirds of Americans with Alzheimer's disease are female.

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.

The researchers were surprised to note that declining awareness of memory loss began earlier in younger participants compared with older participants. 

They suggest that this may reflect a general awareness that memory loss is expected at older ages, rather than indicating an age-related difference in memory loss awareness.

In addition to tracking changes in memory among the participants, the researchers also examined the brains of 385 participants who died during the study. Specifically, the brains were assessed for seven different types of changes that frequently occur in brains affected by dementia.

Three of these changes were associated with a rapid decline in memory loss awareness. These were the accumulation of tau protein (tau tangles), areas of brain damage (infarcts) and changes in the transactive response DNA-binding protein 43 (TDP-43) pathology.

The researchers conclude that friends and family are vital for the care of people who could be developing a case of dementia:

"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."

References:

1.  Temporal course and pathologic basis of unawareness of memory loss in dementia, Robert S. Wilson et al., Neurology, published online 26 August 2015, abstract.
2.  American Academy of Neurology news release, accessed 24 August 2015.
3.  Additional source: Alzheimer's Association, 2015 Alzheimer's disease facts and figures, accessed 24 August 2015.
4.  Additional source: Mayo Clinic, Dementia - definition, accessed 24 August 2015.