Aug. 10, 2011 -- Signs of Alzheimer’s disease tend to be less noticeable in people over 80, suggesting that the condition may be under-diagnosed in the very old.
Researchers examined standard measures of Alzheimer’s by age, finding that older elderly people may have more subtle symptoms of the disease than the younger elderly.
Specifically, people over age 80 showed less difference in brain size compared to healthy peers of the same age. And even though they had similar levels of thinking impairment as younger Alzheimer’s patients, the difference compared to healthy people of the same age was less pronounced.
“Our findings suggest that the changes associated with Alzheimer’s disease may be more difficult to detect in people over the age of 80,” says researcher Mark Bondi, who directs the neuropsychological assessment unit at the VA San Diego Health Care System. “We may be missing mild cases of Alzheimer’s in this age group.”
People over age 80 make up the fastest-growing population in the world. By the year 2040, it is projected that 3.5% of the U.S. population will be 85 or older, compared to less than 2% today.
The study by Bondi and colleagues included 105 people with a diagnosis of Alzheimer’s disease and 125 people with no such diagnosis. Participants were grouped according to age, as younger old (aged 60 to 75) or older old (80 and older).
All the study participants were given standardized mental ability tests that measured language, attention and information processing speed, memory, and ability to manage tasks.
They also had brain scans to measure the thickness of the outermost tissue layers in the part of the brain known as the cerebrum. Cerebrum thinning and thinning in other key regions of the brain are routinely assessed in the diagnosis of Alzheimer’s and other age-related memory disorders.
Even though the younger old and older old patients had similar overall declines, the pattern of change associated with a diagnosis of Alzheimer’s was found to be less noticeable in the patients who were 80 and older.
In the older participants, there was less difference in memory and other measures of cognitive function between people with a diagnosis of Alzheimer’s and people in the same age group without a diagnosis than in the younger age group.
The older Alzheimer’s patients also showed less severe thinning of portions of the cerebral cortex and the overall cerebrum than the younger patients when compared to healthy peers.
Bondi says this is not surprising because decreases in the thickness of these areas of the brain have been found to occur with normal aging.
The study appears online today in the journal Neurology.