Aging: To Treat, or Not to Treat?
The possibility of treating aging is not just an idle fantasy
Why One Threat at a Time?
The realization that aging can be manipulated has profound implications for people. Controlled reduction of food intake (dietary restriction) can improve late-life health and increase lifespan in mammals, from rodents to rhesus monkeys. Whether it might do the same in humans is currently under investigation. One aim of aging research is to develop drugs that can reproduce the effects of dietary restriction and also of genetic alterations that slow aging. One approach could be to use drug therapy to target the nutrient-sensitive pathways that regulate aging (for example, TOR) and that seem to mediate the effects of dietary restriction on aging. The ultimate goal would be a pill that one could take regularly from midlife onward. This pill would theoretically slow aging with minimal side effects. Its predicted impact would be to reduce the incidence of aging-related disease at all ages—although not to remove them altogether. This would lengthen good health later into life and extend our lifespan—possibly without expanding periods of disability and dependency.
Such an approach could revolutionize the ways that diseases of aging are combated. Currently they are, by and large, tackled individually. One scientist studies heart disease, another Alzheimer’s disease, another macular degeneration and so on. Yet such ailments are symptoms of a larger underlying syndrome: aging. It is for this reason that there is a law of diminishing returns when it comes to treating diseases of aging. The battle with aging is akin to that between Heracles, the hero of Greek mythology, and the multiheaded Hydra. Each time Heracles hacked off a head, two more would sprout in its place. Likewise, the old man successfully treated for prostate cancer may not long afterward stagger back into the physician’s office with macular degeneration and dementia. Such piecemeal approaches to treating age-related illness have undoubtedly improved late-life health to an extent and they have increased life expectancy. This, again, is something to celebrate. Yet in the long run a more powerful way to protect against age-related disease would be to intervene in the aging process itself. This would provide protection against the full spectrum of age-related illnesses. Returning to our classical illustration, to really defeat the diseases of late life we need to strike at the heart of the Hydra of senescence: the aging process itself. But is this actually where biogerontology is headed?
After establishing my own research laboratory some years ago, I found myself brooding about the purpose of biogerontology. As a scientist working on aging, what exactly should I be trying to achieve? What was the big plan? I began asking other biogerontologists and soon discovered that there was no unified vision regarding what to do about aging once we understood it. I realized that I’d have to try to figure this out for myself. It helped that a few people had wondered about this before, particularly in medical ethics. In 2003 Eric Juengst at Case Western Reserve University identified three distinct goals for biogerontology. One he called compressed morbidity. This entails improving late-life health while avoiding any major extension of lifespan. Another was arrested aging, that is to say, stopping aging altogether. And the third was decelerated aging, slowing down the aging process. Putting aside the question of the pros and cons of each goal, only decelerated aging seemed plausible to me, given recent developments in biogerontology.
But is this a type of medicine that humanity should pursue? As I see it, decelerating human aging would have two outcomes in ethical terms. On the one hand, it would reduce disease on an enormous scale. This would be a great good. On the other hand, it would lead to life extension, perhaps eventually of a large magnitude. This second outcome is controversial. Surveys of public opinion, for example by researchers at the University of Queensland in Australia in 2009, suggest that most people would favor this outcome, but not all. There have been some vocal opponents. Yet, given the great benefit of decelerated aging in terms of reduced suffering, I feel we must pursue this approach, despite the misgivings.