US researchers have combined data from three longitudinal studies to reveal that a person’s ability to recognise their memory is failing drops in the two to three years prior to receiving a diagnosis of dementia.
The findings shed more light on how the condition affects people’s perception of their own memory abilities, and is published on 26 August in the journal Neurology.
Caregivers of people with dementia will often report that their loved ones lack an awareness of the increasing memory and thinking difficulties they’re experiencing. Some studies have tried to measure this in people with dementia, but the follow-up times in these studies have been short. To overcome this, a team from Rush University Medical Center in Chicago combined data from 2,092 people in 3 longitudinal population studies in the US.
None of those enrolled at the start of the study had memory and thinking problems or dementia, and had an average age of 76. Participants had yearly assessments including medical history and cognitive tests. At each assessment, they were also asked to rate their own memory skills by responding to the questions: “How often do you have trouble remembering things?” and “Compared to 10 years ago, would you say that your memory is much worse, a little worse, the same, a little better, or much better?”.
At the start of the study, participants’ ability to rate their own memory mirrored their performance on cognitive tests. Over the course of the study, which followed volunteers for an average of almost eight years, 239 people developed dementia and had completed four follow-up assessments. The team studied how their perception of their memory performance altered over time. They found that awareness of memory problems declined markedly around two and a half years before a diagnosis of dementia, although the timing and speed of the decline varied between individuals. Memory awareness in older participants (average age of 87) began to decline 2-3 years later than in younger individuals (average age of 70), which the authors suggest could be related to heightened awareness of abnormal memory changes in those of a younger age.
Of the volunteers who took part in the study, 385 also agreed to donate their brains to research after death. The team found that a decline in awareness of memory problems was associated with higher levels of hallmark dementia changes in the brain. These included the presence of blood vessel damage, clumps of a protein called tau, and levels of another protein called TDP-43.
Dr Laura Phipps of Alzheimer’s Research UK, the UK’s leading dementia research charity, said:
“It’s not an easy task to track people over time before a diagnosis of dementia, and this study presents interesting insights into the changes taking place in the early stages of the condition. The findings show that it’s common for people to lose the ability to recognise the memory difficulties they’re experiencing in the lead-up to a diagnosis and suggests that this is driven by underlying damage in the brain. The findings highlight the importance of testimony from relatives and close friends at the point of diagnosis to help doctors to gain a clearer picture of someone’s memory problems.
“Dementia affects everyone differently but it is a progressive condition, which often has a slow and subtle onset. This study only focused on memory changes and it will also be important to track other early signs of dementia in the lead up to a diagnosis. Understanding how dementia affects people before in the years prior to a diagnosis will not only give researchers greater insight into the condition but could assist doctors in making a diagnosis. Research to better characterise how dementia affects people over time, particularly in the early stages, is key to driving progress for all those affected by this devastating condition.”