New diagnostic methods may help clinicians differentiate between normal aging and the early stages of Alzheimer’s disease and dementia.
Savannah, GA—Computer-assisted volumetric brain imaging can help to identify dementia and Alzheimer’s disease at the earliest stages, when interventional treatments can have the greatest impact on preserving memory and other intellectual abilities, reported Daniel D. Sewell, MD, University of California, San Diego, at the 2010 Annual Meeting of the American Association for Geriatric Psychiatry. In a review of recent studies, Dr. Sewell discussed the various psychological, cognitive, behavioral, and neuroimaging changes that can help clinicians differentiate between normal, age-related cognitive decline and the early stages of dementia, when intervention may help to stem memory loss.
“Accurately diagnosing dementia at the earliest possible moment using traditional clinical methods such as history gathering and clinical interviewing is very challenging, because it is not so easy to distinguish normal aging from what may be changes signaling very early-stage dementia,” Dr. Sewell told Neurology Reviews. “The identification of potential biomarkers, such as volumetric brain imaging, will permit us to distinguish between the two and allow us to prescribe disease-modifying agents to the people who need them, as early as possible.”
Identifying At-Risk Patients
The courses of cognitive decline in normal aging and early dementia are very similar. Crystallized cognitive abilities typically remain intact, but fluid cognitive abilities begin to wane. “Fluid cognition peaks in the mid-20s, and then begins declining gradually until our 60s, when the rate of decline accelerates,” Dr. Sewell noted. “These abilities decline as a part of normal aging, but in individuals living with dementia, the decline is larger and more rapid than in normal aging.”
In normal aging, a patient may complain about delayed memory retrieval, but with prompts and cues can remember things. In dementia, however, the patient displays true memory dysfunction, in which prompts and cues are of no help. Both individuals with normal aging and those with very early Alzheimer’s dementia may demonstrate overly inclusive thinking and talking with a storytelling type of speech. However, patients with Alzheimer’s disease may experience changes in thinking and speech, such as the inability to form cohesive sentences, marked by tangentiality and “word salad,” or incoherent speech composed of real or imagined words that lack comprehensive meaning, which may not become apparent until later stages of the illness.
In terms of behavioral and psychological changes, the difference between normal aging and early dementia often depends on the degree of change. In normal aging, a person may become more outspoken, be less concerned with what others think, become less aggressive, have mild real or imagined health concerns, be worried about personal safety, and act more cautiously.
Abnormal social and psychological changes that occur later in life include socially inappropriate behaviors or a decline of inhibitions, becoming disrespectful of others, displaying increased hostility and aggression or apathy, having somatic preoccupations or delusions, withdrawing from friends and family, and living with disabling anxiety.
“These behaviors, in and of themselves, would not prove that someone has dementia,” Dr. Sewell cautioned. “But, when coupled with other information, such as a patient’s past history of unusual behavior, would certainly greatly increase a clinician’s index of suspicion that a person was experiencing dementia.”
Assessing Cognitive Function
Adults with age-associated memory impairment typically score one standard deviation below the mean established for young adults on standard memory tests and usually remain within the normal range of cognitive tests, but they may score lower than expected based on their education level. Patients with mild cognitive impairment show more severe changes than those with standard age-related memory decline but still score above the threshold for dementia on the Mini-Mental State Examination.
“Mild cognitive impairment is not necessarily an early manifestation of dementia,” Dr. Sewell noted. “About 20% of these patients never get worse.”
However, each year about 20% of patients with mild cognitive impairment progress to mild dementia, and without interventional treatment these patients typically progress to moderate dementia within two years, based on the Functional Assessment Staging Test.
“By that time, the illness has probably been present for years, and significant brain injury has already occurred,” he said.
Volumetric Brain Imaging
Measuring disease-related brain atrophy using noninvasive volumetric MRI shows promise for both early detection and monitoring of neurodegeneration, as well as providing some reassurance to patients worried about age-related cognitive decline, Dr. Sewell’s colleague, James Brewer, MD, PhD, told Neurology Reviews.
“Volumetric brain imaging is quite helpful for providing an objective assessment of the state of the brain in patients who might be complaining of memory loss,” noted Dr. Brewer, Assistant Professor of Radiology and Neurosciences at the University of California, San Diego. “Given that there is strong evidence that neurodegeneration precedes patients’ complaints, the absence of abnormal atrophy probably suggests that causes other than Alzheimer’s disease, such as depression or medications, should be seriously considered.”