Medical advances and living standards have extended the average human longevity from 48 years in 1955 to 71 years today, and the elderly are now the fastest growing segment of society. But while our life spans are improving, our health spans are not, writes science journalist Sue Armstrong in “Borrowed Time: The Science of How and Why We Age” (Bloomsbury), out now.
“Over the past 50 years, health care hasn’t slowed the aging process so much as it has slowed the dying process,” she writes, quoting gerontologist Eileen Crimmins.
But now scientists are working to reverse or halt the aging process, which could one day prevent ailments like cancer and heart disease, allowing the elderly a new lease on life. “At the moment,” Armstrong says, “people face the prospect of 15 to 20 years of ill health at the end of their lives. The aim … is to keep you healthy and independent until right near the end.”
First, it’s important to understand what’s happening under our skin as we get older.
Over time, our cells keep dividing to help our bodies grow and repair themselves. But after about 50 divisions or so, the cells stop dividing — a mechanism that helps protect us from cancer.
In a normal body, these “zombie” cells (which are produced continually throughout our life spans, not just when we age ) are cleared away by the immune system. But when we get older, the number of zombie cells increases so much that it’s harder for the immune system, which is also aging, to expel them. These elderly cells secrete substances that chew up collagen, writes Armstrong, which holds our cells together and keeps our skin firm, and also cause inflammation, or “constant, low-grade, below-the-radar excitation of the immune system — that is one of the key forces of aging,” she writes.
Right now, scientists are focused on two methods of preventing damage caused by the zombie cells — also known as senescent cells. “One strategy is to develop agents … that will kill the cells … The other is to rejuvenate the cells so that they function normally,” Armstrong writes. “There are pros and cons to each approach.
“There’s always the risk, too, that in trying to limit the damage, you will be tampering with the positive things — some vitally important and some yet to be discovered — that senescent cells do,” she warns.
Scientists have found some success making zombie cells suicidal. In 2016, experts at the Mayo Clinic announced that by giving mice drugs that kill senescent cells, they were able to “clear or prevent the buildup of calcium in blood vessels that leads to cardiovascular diseases.”
“They hope this will translate into new methods of treatment for people with hardening of the arteries to replace or complement surgery,” she writes.
But killing off zombie cells in old people — whose bodies are full of such cells, could be disastrous. “You might have a collapse of all sorts of systems,” says Armstrong. “The mind boggles — it could cause a meltdown.”
The other option — making zombie cells function normally again — has also been effective in lab experiments. But suddenly flipping the switch on cells that have shut down could lead to “an unrestrained damaged cell [that] might turn cancerous.”
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Still, there is some hope. Scientists have found that the drug rapamycin, derived from a soil bacterium found on Easter Island that’s used to prevent organ-transplant rejection, causes zombie skin cells to rejuvenate in the lab.
Of course, like everything else, it comes with side effects, including constipation, swollen ankles and an increase in diabetes.
But by manipulating the dosage — giving it intermittently — scientists might figure out how to block the cell secretions that cause inflammation without blocking the secretions that aid in wound healing.
“We think this could provide a paradigm shift in the treatment of age-related disease, including cancer,” scientist Judy Campisi, a leader in the field of cell-senescence research, says in the book.
Armstrong agrees, arguing, “We really are on the brink of a revolution in how we view aging and how we start trying to treat the ill health associated with it. Nobody is willing to put an exact date on it, but hopefully my grandchildren’s generation will be running marathons in their 80s and 90s as a matter of course, and more people will be reaching 100 years and longer still healthy and independent.”
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