"The female advantage in verbal memory may allow women to maintain normal cognitive function for longer as the disease progresses," said study author Erin Sundermann of Albert Einstein College of Medicine. "And that female advantage may help to mask a true mild cognitive impairment diagnosis in women."
"The finding may be due to the fact that the cognitive tests used are less sensitive to early decline in women and may miss the earliest stages of deterioration," said Mount Sinai Professor Mary Sano, who wrote an accompanying editorial
for the study.
For reasons science doesn't fully understand, women traditionally perform better than men on verbal memory tests. But this study looked at whether that gender difference might be affecting how early a woman is diagnosed with memory loss — and therefore treated.
"Early diagnosis offers better planning opportunities, allows a patient to make choices for themselves while they can, and can put support systems in place earlier," said Sano, who directs Mount Sinai's Alzheimer's Disease Research Center. "That is also the best point at which to target current, as well as experimental, therapeutics."
That's critically important, added Sundermann, because "these interventions seem to be most effective when given at earlier stages of impairment. Thus, the currently available drugs may stand a better chance of slowing progression in women if we can diagnose women at an earlier disease state."
The study looked at 235 patients with an Alzheimer's or dementia diagnosis and compared them to 694 patients with mild cognitive impairment and 379 healthy participants, analyzing both their test results and the size of their hippocampus. The hippocampus is the organ in the brain most responsible for memory; in Alzheimer's it shrinks as the disease progresses.
Not only did women outperform men overall on verbal memory, they continued to do so when their hippocampus was shrunken. Most important, by the time women showed signs of memory impairment, the size of their hippocampus was significantly smaller than a man's. Sundermann believes that might lead to a worse prognosis for women than men.
"Our overarching theory is that once cognitive decline begins, it will occur more rapidly in women compared to men because the disease is more advanced at that point," said Sundermann. "In order to more definitively test this, we need to track individuals' verbal memory performance and brain size across time from the disease stage of normal, to Alzheimer's-type dementia."
While further research is underway, say the authors, there are important changes that could be made to today's diagnostic tools.
"I think we need to rethink our screening and assessment tools to be sure they are equally sensitive to men and women," said Sano. "Better tests could be more sensitive memory tests or other cognitive tests that are more difficult."
"Alternately, in women it might be particularly important to consider self-reported cognitive change, which may precede the change in formal testing," added Sano.