Preventing Alzheimer's: Early Language Abilities May
Protect Memory Decades Later
July 08, 2009
SAN FRANCISCO, July 8 -- Sophisticated language skills early in adulthood may protect against the symptoms of Alzheimer's disease -- even when its characteristic brain lesions are present later on, researchers found.
Women free of memory problems until death showed significantly higher command of the language in their late teens and early 20's than those who developed clinical Alzheimer's, according to Juan C. Troncoso, MD, of Johns Hopkins University, and colleagues.
The importance of these skills -- measured by "idea density" in an essay from early adulthood -- held for women with intact cognition, regardless of whether a brain autopsy showed the hallmark plaques and tangles of Alzheimer's, Dr. Troncoso's group reported online in Neurology.
* Explain to interested patients that the study suggested a link between greater language skills early in life and lack of cognitive impairment late in life but could not prove a causal effect or determine the mechanism.
* Note the small sample size in the language analysis.
The findings add to the evidence that so-called "cognitive reserve" mitigates the effects of neurological disease, commented Robert Stern, PhD, of Boston University, who was not involved in the study.
Language abilities -- like other measures of this reserve used in prior studies, such as years of education -- appear to be surrogate markers for "bigger and better brains," with more connections between neurons, he said.
Rather than decreasing the likelihood that a person will develop Alzheimer's, it apparently staves off some clinical symptoms of the underlying disease, such as memory loss, Dr. Stern added.
Exercising the mind early in life may help build a protective cognitive reserve, although studies like this cannot prove it's effective, commented Samuel Gandy, MD, of Mount Sinai Alzheimer's Disease Research Center in New York.
"The notion of recommending language acquisition as a kind of mental exercise that might lower one's risk for Alzheimer's disease follows logically," he observed.
And even if it doesn't help in the end, language skill certainly can't hurt, he said.
Alzheimer's disease has puzzled researchers because the same degree of damage to the brain causes severe symptoms in some people, but not in others, Dr. Troncoso's group noted.
To determine what factors earlier in life might produce these differences, the researchers looked at a particularly Alzheimer's-vulnerable area of the hippocampus in brain autopsies of 38 Roman Catholic nuns.
These women, all born before 1917, had been part of the larger Nun Study, an ongoing longitudinal study that originally involved 678 American members of the School Sisters of Notre Dame.
Autopsies showed that women with Alzheimer's disease in this cohort had significant atrophy of neuronal cell bodies, nuclei, and nucleoli compared with controls who had no symptoms or brain lesions.
Women with asymptomatic Alzheimer's disease -- who showed no cognitive impairment before death but showed Alzheimer's disease-type brain lesions on autopsy -- had markedly larger compartments of neurons compared with all the other groups of women.
Compared with women who had mild cognitive impairment, those with asymptomatic Alzheimer's disease had:
* 44.9% larger cell bodies (P<0.05).
* 59.7% larger nuclei (P<0.01).
* 80.2% larger nucleoli, which indicate transcription and metabolic
activities in neurons (P<0.01).
Compared with controls, asymptomatic Alzheimer's was associated with:
* 30.9% larger neuronal cell bodies (P<0.05).
* 36.4% larger nuclei (P<0.01).
* 41.9% larger nucleoli (P<0.05).
These changes may indicate that the neurons are repairing themselves or growing and making new connections to compensate for damage, the researchers said.
Across these groups, there were no differences in age at death, education level, or time from last cognitive evaluation to death that could explain the results.
However, language ability earlier in life did appear to correlate with clinical outcomes.
The researchers analyzed essays that 14 of the women had written as they entered the convent five or six decades earlier.
Women without old-age cognitive impairments -- including two with asymptomatic Alzheimer's disease and six controls -- had expressed a significantly higher number of ideas for every 10 words in the essay than did the one patient with mild cognitive impairment and the five with Alzheimer's disease (average score 6.9 versus 5.0).
But the complexity of grammar in the essays did not differ by cognitive ability late in life.
The researchers called this a fascinating observation but cautioned about the small sample size.
Dr. Gandy agreed that the study could not get at the mechanism behind the association. He noted, though, that language skills are complex and exercise sensory, cognitive, and motor areas of the brain at the same time.
They also found that frequency expression of the APOE2 allele was higher in the asymptomatic subjects (30%), compared to those with mild cognitive impairment and those with Alzheimer's disease (3.3%) (P<0.012).
"The difference suggests that the APOE2 allele has the potential to protect the brain from the neurotoxic effects of Aé and tau, and may be associated with the neuronal hypertrophy," the researchers wrote.
The study was supported by the Johns Hopkins University Alzheimer's Disease Research Center, the National Institutes of Health, the Nun Study, the National Institute on Aging, the University of Kentucky Alzheimer's Disease Center, the Abercrombie Foundation and the Kleberg Foundation.
The researchers reported no conflicts of interest. Drs. Gandy and Stern provided no information on conflicts of interest.
Primary source: Neurology
Iacono D, et al "The Nun Study: Clinically silent AD, neuronal hypertrophy, and linguistic skills in early life" Neurology 2009.
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