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Iacono effectively picked up where Snowdon left off. Iacono and his colleagues discovered that not only did nuns who avoided dementia later in life have 20% higher linguistic scores as young women, compared with peers who developed symptoms of cognitive decline, but that the relationship held up even in nuns whose brains showed all the physical signs of Alzheimer's. "There is a special group of people who have comparable amount of plaques and tangles the typical marks of the disease without the cognitive impairment," says Iacono. "[It appears that] people with higher linguistic scores were protected even in the face of higher pathology."
The finding adds to a collection of studies suggesting that the greater one's initial mental fitness measured variously as higher educational achievement or high IQ, for example the better it may be safeguarded in old age. "It's broadly consistent with the notion that if someone starts out with the ability, however their brain is organized, to have a greater set of skills in language and performing other complicated tasks, then maybe that brain is more resistant [later in life]," says Harvard's Hyman.
How exactly the brain builds up resistance to Alzheimer's is, of course, the central question driving legions of researchers. Are some people's brains capable of building detours around damaged neural circuits? Is there a gene that may help certain people rebuild and repair damaged brain tissue better than others can? Iacono suggests that's a strong possibility, pointing to the presence of one particular gene, APOE2, in 30% of patients with asymptomatic Alzheimer's. The next step in his research, he says, is to understand how this gene works.
What researchers are increasingly discovering is that the human brain may contain much more plasticity than they thought. Understanding how it recovers from injury or compensates for damaged tissue may shed light not only on memory disorders, but also on other conditions, such as Parkinson's or Lou Gehrig's disease, Hyman suggests. "That kind of mental flexibility would be an important component to recovery from any kind of damage."
It is not yet clear whether highly developed language skills actually play a role in fending off Alzheimer's disease or whether the correlation is merely a side effect of other protective processes. Indeed, Iacono's study, which involved 38 nuns, only 14 of whom he had writing samples from, is too small to show a definitive effect. But the way Iacono looks at it, no one knows how much of the risk of dementia is hardwired into our DNA and how much is determined by environmental factors like physical exercise and social activity, so while the jury is still out, brushing up on your Shakespeare certainly can't hurt.