Young people with limited language ability are at higher risk of developing Alzheimer's disease in old age than those capable of verbal acrobatics. Researchers KU and the University of Kentucky reported this finding in the Feb. 21 issue of the Journal of the American Medical Association. Their study focused on 93 nuns who are members of the School Sisters of Notre Dame, a religious congregation.
"These are sisters in retirement, for the most part," said Susan J. Kemper, KU professor of psychology and research associate at the KU Gerontology Center. "All of them were born in 1916 or before."
Kemper analyzed the nuns' language skills in early adulthood, working from samples of their writing. Researchers at the University of Kentucky assessed the nuns' cognitive skills in old age. And the nuns who've died have been the subject of post-mortem autopsies at Kentucky to establish the presence or absence of Alzheimer's.
Susan J. Kemper
The study suggests that people who, in their youth, produce sentences that are grammatically simple and low in idea content have a higher risk of developing cognitive impairments in old age, compared with those who use more grammatically complex and idea-dense sentences.
David Snowdon, professor of preventive medicine at the University of Kentucky, launched what is called the Nun Study in 1986, Kemper said, with recruitment efforts among the Notre Dame sisters.
The nuns agreed to an annual physical exam and assessment of their mental capabilities. They opened their convent files to him, which included samples of their writing and agreed to donate their brains for study after their deaths.
Sixty-six percent who were asked to participate agreed to do so, Kemper said. The 93 in the current study are only a portion of the total of 678 who signed on and who will be studied for years to come. All 93 nuns had produced, at an average age of 22, autobiographies of 250 to 300 words, Kemper said. These were the basis for her analysis.
Snowdon and three other University of Kentucky colleagues working on the project - Lydia Greiner, David Wekstein and William Markesbery - are affiliated with the university's Sanders-Brown Center on Aging.
James Mortimer, professor of preventive medicine at the University of South Florida, helped in conceptualizing the project.
The University of Kentucky team used neuropsychological and physical function tests to determine the presence of dementia in the nuns. To date, post-mortem autopsies have been performed on 25 nuns to confirm whether the dementia was due to Alzheimer's disease or other diseases or neurological conditions.
In her analysis, Kemper graded the language of the autobiographies in grammatical complexity and "idea density."
A sentence like "Jill met Jack" is grammatically simple. A sentence like "Jill, a computer operator, met Jack, who had been visiting Jill's mother" is more grammatically complex.
To illustrate idea density, Kemper contrasted the sentence "Jack made Jill a doll" with the sentence "Jack made Jill smile." The grammar in both sentences is relatively simple, but the second sentence has more idea density.
In the first sentence, all the ideas are made explicit by the words. In the second, a suggestion exists that Jack had to do something to prompt Jill's smiling, so there are more ideas present than are represented by the words. The nuns whose youthful writing showed low idea density had a dramatically higher incidence of Alzheimer's in old age, Kemper said.
According to the the Journal of the American Medical Association paper, the post-mortem analysis on the 25 nuns indicated that 10 had Alzheimer's disease. Nine of those 10 evinced low idea density in their autobiographies. The other 15 sisters did not show signs of Alzheimer's - and only two of them showed low idea density in their autobiographies.
Some scientists theorize that higher education may afford some protection against Alzheimer's. The current study shows that any such protection is not absolute. Most of the 93 sisters in the study were college-educated.
The question is, Does the production of complex and idea-dense sentences in early life shore up the brain against later ruin? Or is the ability to form such sentences evidence of an inherent protection that exists before such language use begins?
Nobody knows the answer to this chicken-or-egg question, Kemper said.
"It's possible that if your mother read to you, if you were engaged as a conversational partner at the supper table, if you had good language abilities when you entered school and that meant you were often called on by the teacher and talked to by playmates," Kemper said, "those may be protective experiences against developing Alzheimer's."
Or perhaps what we are seeing are the first early signs of Alzheimer's affecting language abilities in young adulthood long before other manifestations of this disease are apparent. Alzheimer's may be a disease that starts in infancy and gradually worsens during the lifespan.
"It's speculative, but you might want to identify individuals at risk and help them develop some of these linguistic skills so as to strengthen the brain and make it more resistant to the disease process. You want to start that intervention as early as possible - and continue it," Kemper said.