Abstracted from “A Scientist’s View of Almost Everything” by Mark M. Green
There was an article in Science dated August 5, 2005 entitled, “Preventing Alzheimer’s: A Lifelong Commitment.” Science is a highly regarded magazine read by almost all scientists and from every discipline of science.
The article begins by talking about research on how intellectual activities and education seem to be connected to a decrease in the risk of Alzheimer’s disease. One prominent study was carried out on a group of Catholic priests, nuns, and brothers who were studied while still alive and had agreed to donate their brains when they died. A battery of tests revealed that higher levels of education better maintained cognitive ability in the participants of the study. And analysis of the brains of these people after death showed that more highly educated participants needed to develop five times as many plaques in their brains (plaques are the signature feature of Alzheimer’s) before showing evidence of the disease while they were alive.
Other studies show that behavior in one’s life can affect the onset of the disease: leisure that requires mental activity such as reading, puzzles, cards, board games, crafts, appear to protect against Alzheimer’s. But leisure activity that is not intellectually demanding such as watching television excessively increased the likelihood of developing Alzheimer’s.
It also seems that physical activity may protect against Alzheimer’s disease. Two prominent studies, one involving 6000 women over the age of 65 and one following over 18,000 women aged from 70 to 81, showed that women who got the most exercise, and that includes walking, showed less cognitive decline over the years. In particular, participants in the study with four or more physical activities including gardening, jogging or biking had about half the risk of dementia as people who engaged in one or no special physical activity. But there is a catch. People who are genetically disposed to Alzheimer’s, who carry a gene known to be associated with the disease, are not much helped by these activities.
Use your brain and exercise your body! Not bad advice in general and probably what most of us would have heard from our ancestors long before epidemiological studies looked into this problem of the aged, a problem associated with the fact that we tend to live a lot longer than those who came before us.
Alzheimer’s disease belongs to a class known as conformational diseases such as Parkinson’s disease. Others found in animals are bovine spongiform encephalopathy, that is, mad cow disease, named for the cow’s behavior. Another important conformational disease is scrapie, afflicting sheep and named for the sheep’s behavior in leaning against a fence for example for support and scraping off their wool coat. And then there is kuru, which means trembling, a degenerative brain disease that is known to be transmitted by ritual cannibalism seen among the people of New Guinea.
Conformation is a term used in the molecular sciences to describe the shape taken by a molecule. Proteins consist of very long molecules, like a long chain but on a still unimaginably small—molecular dimension. Imagine the kinds of metal chains we are all used to dealing with. Throw the chain to the ground over and over and each time the chain will take a different shape or in molecular words a different conformation. There is nothing particular in the chain we buy in a hardware store to favor taking one shape or another. But protein chains are different. A protein chain does not take a random shape when it is let loose from the body’s machinery that made it. Each protein has a particular shape that it folds into, although there are small disordered regions within that shape, which have different important functions. And this shape, this conformation, is the only one that allows that particular protein to do its intended job. As long as the protein chain maintains that shape all is well.
But in conformational diseases for reasons that are not well understood certain proteins lose their intended shape and this shape change causes them to glom together and to form what are called plaques, which are deposits that sit in our brains and block necessary biological functions. And even worse is that when one of these proteins changes into this glom-loving form it acts like a pied piper and causes other normal proteins to follow its example. And so, slowly, over long periods of time, many of the proteins carrying out essential tasks are lost and this loss occurs faster and faster as more and more protein chains join in.
Recently research carried out at the University of Rochester has uncovered a system in the brain, termed glymphatic, that acts to clear out the debris associated with the formation of these badly folded proteins, so-called misfolded proteins. Importantly, the glymphatic system has been discovered to most likely carry out its function during parts of our deepest sleep, non-rapid eye movement sleep, NREM, that sleep when we don’t dream for example. Sleep that is interrupted blocks our entry into NREM sleep. The research suggests however that exercise increases the activity of the glymphatic system, therefore perhaps compensating to some extent for this loss of the function of NREM sleep, consistent with one of the behavioral activities helping to avoid dementia.
Perhaps Shakespeare had it right about sleep: “Balm of hurt minds, great nature’s second course.”