Women may be more likely to develop Alzheimer's disease, but men are typically diagnosed at earlier stages, when symptoms are mild. By tweaking memory tests a little, more women might be caught at an early stage of the disease, when they can benefit from treatment, a study suggests.
Adjusting the test scoring to take into account women’s lifelong advantage in verbal memory performance allows researchers to identify more women with the Alzheimer’s precursor, amnestic mild cognitive impairment, or aMCI, according to the report published Wednesday in Neurology.
Verbal memory refers to the ability to memorize information, to remember words and to recall stories. The same verbal ability that allows women to score higher on memory tests also helps them to compensate for the damage that Alzheimer's does to their brains for a longer period of time, the research indicates.
But there is a point at which they can't compensate any more and then they develop symptoms faster.
“The female advantage in verbal memory may actually put women at a disadvantage when it comes to diagnosing Alzheimer’s at an early stage,” said the study’s lead author, Erin Sundermann, an assistant project scientist in the department of psychiatry at the University of California, San Diego, School of Medicine. “If we just adjust the criteria to be sex specific to account for this female advantage, our results suggest it would improve diagnostic accuracy in both women and men.”
That means women wouldn’t be the only ones to benefit. With the previous criteria, 10 percent of men would be wrongly identified as having aMCI. They now would be in the normal category. At the same time, another 10 percent of women would be added to the ranks of those with an aMCI diagnosis.
For women, early diagnosis means more time to plan for the future when symptoms are mild and an opportunity to make lifestyle changes — such as improving diet and increasing exercise — that might slow the disease's progress, Sundermann said.
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More precise diagnoses in men and women would also help improve accuracy in clinical trials of potential therapies, she said.
“About 20 percent diagnostic errors could really dilute important findings,” in research, she said.
Without correcting for the female verbal memory advantage, women tend to be diagnosed at a later stage of the disease, at which point, they progress very rapidly, Sundermann said.
The verbal advantage allows women “to hang on longer," she said. "But once the brain changes surpass their ability to compensate, they tank and decline faster.”
Understanding sex differences in Alzheimer's
For the new study, Sundermann and her colleagues analyzed data from 453 women and 532 men who were participants in the Alzheimer’s Neuroimaging Initiative. The researchers rescored verbal memory tests with the new criteria and then looked at how well the newly scored results fit physical findings, such as biomarkers, including those measuring levels of abnormal proteins in cerebrospinal fluid, and scans designed to show how much abnormal protein might be gunking up people’s brains.
The researchers found that the biomarkers and brain scans backed up their new diagnoses. With the new criteria, women who would be considered positive for aMCI had brain scans and biomarkers that indicated the beginnings of Alzheimer’s. Men who would currently be considered normal had biomarkers and brain scans that agreed with that diagnosis.
The new study “is a persuasive first step, showing that correcting for sex differences in verbal memory performance seems to better align with the underlying biology of Alzheimer’s disease,” said Beth Snitz, an associate professor of neurology at the University of Pittsburgh and a neuropsychologist at the university’s Alzheimer Disease Research Center.
“There is a lot of interest in sex differences in Alzheimer’s disease and in drilling down to understand them,” Snitz said in an email.
While some people might not want to know about the early signs of Alzheimer's, the new findings could help more women when they can still make plans for the future, experts said.
"As your memory becomes more impaired, you are less and less aware you are having memory problems," said Sandra Weintraub, a professor of psychiatry and behavioral sciences and the clinical board director of the Mesulam Cognitive Neurology and Alzheimer’s Disease Center at Northwestern University’s Feinberg School of Medicine. "That is the worst time to plan.”