Decrease in Risk of Alzheimer’s Disease

The sophistication of language abilities attained in a person’s early twenties may predict the risk of developing dementia later in life. Alzheimer’s is the most common form of dementia, and is linked to the development of protein plaques and nerve cell tangles within the brain. However, scientists have questioned why these signs of damage cause symptoms of dementia in some people, but not in others.

To find out, a research team from Johns Hopkins University in Baltimore recently conducted an analysis on the brains of 38 deceased Catholic nuns. The women had been participants in an ongoing clinical study known as the Nun Study. The researchers discovered that those with good language skills early in life were less likely to have memory problems. This was found to be true even if signs of dementia damage were observed in the brain. The study was published online in the journal Neurology.

For the analysis, the women were divided into two groups of those who had experienced memory loss and had signs of dementia damage in the brain, and those who had not experienced memory loss whether their brains had signs of dementia damage or not. The brains of those women without Alzheimer’s symptoms were found to contain larger neurons than those who suffered memory loss. The researchers noted that there is a possibility that the larger neurons compensated for the brain plaques and tangles that are commonly indicative of Alzheimer's disease.

The researchers also analyzed essays written by 14 of the women during their late teens or early twenties and assessed the complexity of language and grammar contained in them. Results of this analysis revealed language scores 20 percent higher in women free of memory problems when compared to those women who had suffered memory problems.

No differences in grammar scores were noted among the women. However, the findings could indicate that early language abilities may well protect memory decades later. According to study author Dr. Diego Iacono, a research fellow in neuropathology at Johns Hopkins University, “We think this percentage could be higher if we could increase the sample size of the subjects to examine. We are working on that.”

In a prior study of men, larger neurons were found in the brains of those with plaques and tangles who showed no evidence of memory loss, leading the researchers to theorize that a growth in brain cells could an early response by the body to the onset of dementia that may help to protect against damage to memory function. It remains unclear as to whether that protection is a result of genetic factors or more intense studies during early adulthood, although it coincides with the cognitive reserve theory involving the mind's resilience to neuropathological damage of the brain.

Regarding the study and its results, lead researcher Dr Juan Troncoso said, “Despite the small number of participants in this portion of the study, the finding is a fascinating one.” He went on to explain, “Our results show that an intellectual ability test in the early twenties may predict the likelihood of remaining cognitively normal five or six decades later, even in the presence of a large amount of Alzheimer's disease pathology.” In addition, he noted, “Perhaps mental abilities at age 20 are indicative of a brain that will be better able to cope with diseases later in life.”

Rebecca Wood, chief executive of the Alzheimer's Research Trust, said, “One possible implication of this study is that an intellectual ability test in the early 20s may predict the likelihood of remaining cognitively normal five or six decades later.” She then pointed out, “However, prominent exceptions exist, including authors like Terry Pratchett and Iris Murdoch, who developed dementia despite their linguistic brilliance.”

The study results also suggested an increased risk for cognitive impairment in people having the APOE4 gene while indicating a protective effect in those having the APOE2 gene. The researchers are now exploring the possibility of a connection between language skills and these genes.

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