Summary: Verbal tests for MCI might not pick up symptoms in women until they are further along into the progression of Alzheimer’s disease, researchers report.
Women may have better verbal memory skills than men even when their brains show the same level of problems metabolizing glucose, which occurs in people with Alzheimer’s disease, according to research published in the October 5, 2016, online issue of Neurology.
“Women perform better than men on tests of verbal memory throughout life, which may give them a buffer of protection against losing their verbal memory skills in the precursor stages of Alzheimer’s disease, known as mild cognitive impairment,” said study author Erin E. Sundermann, PhD, of the University of California, San Diego, who conducted the research while at Albert Einstein College of Medicine in Bronx, NY. “This is especially important because verbal memory tests are used to diagnose people with Alzheimer’s disease and mild cognitive impairment, so women may not be diagnosed until they are further along in the disease.”
The study included people from the Alzheimer’s Disease Neuroimaging Initiative: 254 people with Alzheimer’s disease, 672 people with mild cognitive impairment that included memory problems and 390 people with no thinking or memory problems. Participants’ verbal memory skills were tested and PET brain scans measured how well their brains metabolized glucose, which is the primary energy source for the brain. Poor metabolism is a sign of dysfunction in brain cells.
The memory test asked participants to remember a list of 15 words read to them, both right away and 30 minutes later. Women scored better than men on the memory tests when they had no, mild or moderate problems with brain metabolism. Once the participants had more advanced metabolism problems, there was no difference in test scores between women and men.
“These results suggest that women are better able to compensate for underlying changes in the brain with their ‘cognitive reserve’ until the disease reaches a more advanced stage,” Sundermann said.
The immediate recall test has a maximum score of 75; memory is considered impaired when scores are less than 37. The study looked at a rate of glucose metabolism in the temporal lobe (brain area responsible for memory function) relative to glucose metabolism in the pons/cerebellum (brain area where metabolism remains stable with increasing age and pathology). This temporal lobe glucose metabolism rate ranges from one to four, with lower scores indicating more dysfunction in brain cells.
In the study, women reached the impaired scores at a lower metabolism rate than men, or a temporal lobe glucose metabolism rate of 2.2 compared to 2.6. The delayed recall test has a maximum score of 15 and scores of less than eight are considered impaired. Women in the study had impaired scores at a glucose metabolism rate of 2.9 compared to 3.7 for men.
“If these results are confirmed, adjusting memory tests to account for the differences between men and women may help diagnose Alzheimer’s disease earlier in women,” Sundermann said.
Sundermann said limitations of the study include that it was a snapshot in time, with one set of tests and images that do not show changes over time, and that most of the participants were white and well educated, so the results may not be relevant to the overall population.
Funding: The Alzheimer’s Disease Neuroimaging Initiative was supported by the National Institute on Aging, National Institute of Biomedical Imaging and Bioengineering, Alzheimer’s Association, Alzheimer’s Drug Discovery Foundation, U.S. Food and Drug Administration, Abbott, Amorfix Life Sciences, AstraZeneca, Bayer HealthCare, BioClinica, Biogen Idec, Bristol-Myers Squibb, Eisai, Elan Pharmaceuticals, Eli Lilly, F. Hoffmann-La Roche and Genentech, GE Healthcare, Innogenetics, IXICO, Janssen Alzheimer Immunotherapy Research and Development, Johnson and Johnson Pharmaceutical Research and Development, Medpace, Merck, Meso Scale Diagnostics, Novartis Pharmaceuticals; Pfizer, Servier, Synarc and Takeda Pharmaceutical.
Source: Renee Tessman – AAN
Image Source: This NeuroscienceNews.com image is in the public domain.
Original Research: Abstract for “Female advantage in verbal memory: Evidence of sex-specific cognitive reserve” by Erin E. Sundermann, Pauline M. Maki, Leah H. Rubin, Richard B. Lipton, Susan Landau, Anat Biegon, and For the Alzheimer’s Disease Neuroimaging Initiative in Neurology. Published online October 5 2016 doi:10.1212/WNL.0000000000003288
Female advantage in verbal memory: Evidence of sex-specific cognitive reserve
Objective: We investigated sex differences in verbal memory across different levels of neural dysfunction, measured by temporal lobe glucose metabolic rates (TLGluMR).
Methods: Three hundred ninety controls and 672 participants with amnestic mild cognitive impairment (aMCI) and 254 with Alzheimer disease (AD) dementia from the Alzheimer’s Disease Neuroimaging Initiative completed the Rey Auditory Verbal Learning Test (RAVLT) and [18F]-fluorodeoxyglucose–PET. Cross-sectional analyses were conducted using linear regression to examine the sex by TLGluMR interaction on RAVLT performance in the overall sample and within diagnostic groups adjusting for age, education, and APOE ε4 genotype.
Results: Across groups, female sex and higher TLGluMR and their interaction were associated with better verbal memory (p values ≤ 0.005). The female advantage in verbal memory varied by TLGluMR such that the advantage was greatest among individuals with moderate to high TLGluMR and minimal or absent among individuals with lower TLGluMR. Diagnosis-stratified analyses revealed that this interaction was driven by the aMCI group (p values = 0.009). The interaction was not significant in control and AD dementia groups.
Conclusions: Women show better verbal memory than men in aMCI despite similar levels of brain hypometabolism. The lifelong advantage that females show over males in verbal memory might represent a form of cognitive reserve that delays verbal memory decline until more advanced pathology, as indexed by TLGluMR. This issue is clinically important because verbal memory scores are used in diagnosing aMCI and AD dementia.
“Female advantage in verbal memory: Evidence of sex-specific cognitive reserve” by Erin E. Sundermann, Pauline M. Maki, Leah H. Rubin, Richard B. Lipton, Susan Landau, Anat Biegon, and For the Alzheimer’s Disease Neuroimaging Initiative in Neurology. Published online October 5 2016 doi:10.1212/WNL.0000000000003288