Memory Decline More Rapid in Women Than Men

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Differences in brain structure, disease progression and biological characteristics may play a role.
Differences in brain structure, disease progression and biological characteristics may play a role.

WASHINGTON — Women with mild cognitive impairment experience memory declines twice as fast as men, according to researchers.

Women's scores on the Alzheimer's Disease Assessment Scale-cognitive sub scale (ADAS-Cog) declined at an average rate of 2.3 points per year (N=141) compared with 1.05 in men (N=257), data from the Alzheimer's Disease Neuroimaging Initiative (ADNI) indicate.

The differences in ADAS-Cog scores between genders was highly significant (P=0.005) after adjustment for age, education, baseline mini mental state examination (MMSE), follow-up time and ApoE4 status. ApoE4 was associated with faster rates of decline in both men and women, the researchers found. Mean follow-up was four years. 

“These results point to the possibility of as yet undiscovered gender-specific genetic or environmental risk factors that influence the speed of decline,” study researcher Katherine Amy Lin of Duke University Medical Center in Durham, North Carolina, said at the 2015 Alzheimer's Association International Conference.  

In a second study, Katie Schenning, MD, MPH, from the Oregon Health & Science University in Portland and colleagues reported that among older patients, women exposed to general anesthesia during surgery declined on measures of cognition, functional status, and brain volumes at significantly faster rates than men and that the difference was more pronounced for women who underwent multiple procedures. 

The retrospective cohort analysis involved data from the Oregon Brain Aging Study and the Intelligent Systems for Assessing Aging Changes, which included 182 people who underwent a total of 331 procedures with general anesthesia. 

Men experienced cognitive declines after exposure to general anesthesia compared with their unexposed counterparts on the MMSE (P=0.009), the Instrumental Activities of Daily Living (P=0.024), and the Clinical Dementia Rating-sum of boxes (CDR-SM, P=0.027), the researchers found.

However, the declines observed among women were significantly more rapid on the following outcomes: MMSE (P<0.001 in women), CDR (P=0.003), CDR-SB (P<0.001), Activities of Daily Living (P<0.001), Delayed Logical Memory (P=0.011) and ventricular volume (P=0.005).

“This is one of the first studies to suggest that among older adults, women are at a higher risk for postoperative brain dysfunction than men,” Scheming said. “Our research clearly shows an association between surgery, general anesthesia and cognitive decline in older adults.”

She called for more studies to confirm the finding, as well as to determine if certain people are more susceptible to postoperative cognitive decline, and whether sex or genetic risk factors play a role in that susceptibility. 

Alzheimer's disease is known to disproportionally affect women — almost two-thirds of Americans with the disease are women. By the age of 65 years, women have a one-in-six risk of developing Alzheimer's compared with a one-in-11 chance for men. 

"[T]here is an urgent need to understand if differences in brain structure, disease progression and biological characteristics contribute to higher prevalence rates and rates of cognitive decline," said Maria Carrillo, PhD, the Chief Scientific Officer of the Alzheimer's Association. 

References

  1. Lin KA et al. #P4-108. “Marked Gender Differences in the Rate of Cognitive Decline in Subjects at Risk for Alzhiemer's Disease."
  2. Schenning K et al. #P1-264. “The Role of Sex in Postoperative Cognitive and Functional Decline."
  3. Both presented at: Alzheimer's Association International Conference 2015. July 18-23, 2015; Washington, D.C. 

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