WEDNESDAY, July 8 (HealthDay News) -- Women with greater language abilities in early adulthood were less likely to have Alzheimer's disease later in life, even when autopsies revealed the clear brain changes that are hallmarks of the disease.
Also, the brains of women without symptoms of Alzheimer's housed bigger neurons, according to a study appearing in the July 9 online edition of Neurology.
"We noticed that the neurons in this group of people are larger and we also know that the same group of people we call asymptomatic also had higher language skills during their 20s," said study author Dr. Diego Iacono, a research fellow in neuropathology at Johns Hopkins University in Baltimore.
It's possible that the larger neurons compensated for the brain plaques and tangles that are usually indicative of Alzheimer's, the authors stated.
The findings could also mean that language abilities in the early 20s can predict the risk of developing dementia several decades later.
A previous study, this one in men, also found larger neurons in individuals who had plaques and tangles but no clinical evidence of Alzheimer's.
For the current study, researchers examined the brains of 38 deceased Catholic nuns, part of the ongoing Nun Study.
Women were divided into two groups: those with symptoms of memory loss along with plaques and tangles and those with no memory loss whether or not they had plaques or tangles.
Essays written by the women when they first entered the convent in their late teens or early 20s were analyzed for richness of language skills, including how many ideas were expressed per 10 words, number of verbs and adjectives in one sentence and more.
Women without memory problems scored 20 percent higher on language tests (though not grammar tests) than did women with memory issues. "We think this percentage could be higher if we could increase the sample size of the subjects to examine. We are working on that," Iacono said.
"The novelty is that these people were normal [cognitively] but they have Alzheimer's disease pathology like the people with dementia," Iacono said. "It's amazing that, even though you have a certain amount of pathology in your brain, you are not demented. You have some protective mechanism."
It's not clear whether that protection comes from genetic factors or from more studying during the first two decades of life, although it does fit with the "cognitive reserve" theory.
"The idea is that we have a sort of cognitive reserve that we start to increase during our second and third decades of life, and you can spend this reserve when you get older," Iacono explained. "In this way, you can avoid the manifestation of dementia even if you have some pathology. This is something we didn't expect."
"This is the second independent sample with the same result. We're back to the metaphor of the brain as a computer and a muscle," said Dr. Gary J. Kennedy, director of geriatric psychiatry at Montefiore Medical Center in New York City. "In volunteers who had no signs of Alzheimer's but did have the plaques and tangles, the neurons were actually larger and more functional with more connections."
The paper also showed an increased risk for cognitive impairment in people with the APOE4 gene and a protective effect in those with the APOE2 gene.
The authors are now investigating to see if they can show a connection between the language skills and these particular genes.
Visit the Alzheimer's Association for more on this condition.
SOURCES: Gary J. Kennedy, M.D., director, geriatric psychiatry, Montefiore Medical Center, New York City; Diego Iacono, M.D., Ph.D., research fellow, neuropathology, Johns Hopkins University, Baltimore; July 9, 2009, Neurology, online