Two-thirds of Alzheimer’s disease patients are women, and a recent study found a key gender-based difference in how patients perform on memory tests used to diagnose the disease.
Put simply: The study found that women perform better.
Researchers call the findings a “double-edged sword” because, while it means women are resilient, it could also mean physicians are missing the early markers of the disease in women, said Pauline Maki, one of the study’s authors.
“Memory is the setup in Alzheimer’s disease patients and what our field hasn’t recognized is there is a huge gender difference in this ability,” said Maki, a professor of psychiatry and psychology at the University of Illinois at Chicago. “Universally, girls remember more than boys and women more than men. The flip side is men have better spatial ability than women.”
Typically when patients are assessed for Alzheimer’s disease they are given a memory test which challenges them to recite back a list of words read out loud, Maki explained. Despite having an inherent advantage, women are assessed the same way as men, using the same cutoff score for correctly recited words.
Since women perform well on these tests, it could mean their superior cognitive abilities are masking early indicators of Alzheimer’s disease. Although more women have the disease than men, more men have what’s called amnestic cognitive mild impairment – the precursor to Alzheimer's disease.
“It doesn’t make any logical sense,” Maki said. “Is the disease more toxic to women? Or is it something about diagnosing women with Alzheimer’s disease at a later stage and we just think they’re at the same stage as men?”
To find out why women seemed to have a later onset of the disease and yet a more accelerated decline than men, researchers performed memory tests and brain scans on patients with various levels of cognitive functioning. The scans were used to measure the level of beta amyloid, a neurotoxin believed to cause cognitive impairment in Alzheimer’s disease.
Researchers found women outperformed men on immediate and delayed recall memory tests when beta amyloid levels were low to moderate. Once those levels reached a certain threshold, however, women’s performance on memory tests declined rapidly.
“Clinically, why that’s important is we don’t have a cure for Alzheimer’s disease, but we do have drugs to help people function better,” Maki said. Medications used to treat Alzheimer’s disease are most effective when started early in the course of the illness.
“What that means for a woman who is doing well in everyday life is in a memory test we may miss the opportunity to get more function or sustain that function longer because we’re not detecting Alzheimer’s disease at that early stage,” Maki said.
Fortunately, researchers have a “simple” solution: “Use a different cutoff score on a woman than a man,” Maki said.
The cutoff score currently used for memory tests is an average of both men and women’s scores. Sex-specific scores could potentially change the diagnoses of both men and women.
“Since women perform better than men on these memory tests, we could falsely be diagnosing men with Alzheimer’s disease,” Maki said. “Maybe men get diagnosed with Alzheimer’s disease too early and die of something else and have anxiety of developing dementia.”
Researchers plan on studying whether sex-specific cutoff scores will improve Alzheimer’s disease diagnoses through a longitudinal study following patients throughout the course of the disease.
Follow Kristen Thometz on Twitter: @kristenthometz
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