Women's verbal memory advantage may mask cognitive decline

By Lucy Piper

Women with amnestic mild cognitive impairment (aMCI) have better verbal memory skills than their male counterparts during the early stages of hippocampal decline.

The study authors note that women generally have better verbal memory throughout life and this advantage "may represent a greater cognitive reserve in women".

Therefore "the clinical manifestation of verbal memory impairment is delayed until a more advanced level of neurodegeneration in women vs men", they add, which the team says could impact on the sensitivity of measures used to detect dementia and delay diagnosis.

The study included 379 healthy individuals, 694 with amnestic mild cognitive impairment (aMCI) and 235 with AD and dementia who were participating in the Alzheimer's Disease Neuroimaging Initiative.

Overall, the 579 women participating in the study significantly outperformed the 729 men on Rey Auditory Verbal Learning Test (RAVLT) for immediate (38.1 vs 32.7) and delayed recall (5.1 vs 3.8).

The magnitude of this female advantage was dependent on the level of neurodegeneration, as indicated by the hippocampal volume/intracranial volume ratio (HpVR). Women with moderate to large HpVR (indicating minimal to moderate neurodegeneration) significantly outperformed men with similar HpVR on both immediate and delayed recall, whereas there was no advantage for women with smaller HpVR indicative of greater neurodegeneration.

This difference was significant among the 285 women and 409 men with aMCI but not between the 107 women and 128 men with AD and dementia or the healthy 187 women and 192 men, the researchers note in Neurology.

Among healthy individuals, women significantly outperformed men irrespective of HpVR, while among patients with AD and dementia, women significantly outperformed men in immediate but not delayed recall.

"These results suggest a diminution of the female advantage but not an elimination," Erin Sundermann (Albert Einstein College of Medicine, New York, USA) and co-workers observe.

They also found that at a RAVLT cutoff score associated with verbal memory impairment, women overall had smaller HpVR than men with the same score.

"If replicated, our findings suggest the need to evaluate whether diagnosis of aMCI is made at a later disease stage in women compared to men because this sex-specific advantage in verbal memory masks underlying neurodegeneration.

"If so, then sex-based norms in clinical memory tests might improve diagnostic accuracy in women."

In a related editorial, Mary Sano (Icahn School of Medicine at Mount Sinai, New York, USA) and Sam Gandy (Veterans Affairs Medical Center, New York, USA) say that in addition to improving detection of meaningful cognitive change in women, increased research and attention in this focused area is necessary to prevent the potential healthcare costs of underdetection or delayed diagnosis of women with prodromal or overt dementia.

"It is ironic that women are disadvantaged by their superior brain volume and cognitive function, which apparently lead to delay in disease detection", they conclude.

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