The field of aging research could do with more of its scientists choosing to write for laypeople; the more outreach the better. This short column by researcher Steven Austad illustrates one way of looking at aging - that it is all about the mortality rate at a given age, and the inexorable rise of that mortality rate over time, caused by the accumulation of cell and tissue damage. By this metric an individual at age 40 or 50 is already significantly impacted by the processes of aging in comparison with an individual at age 20, manifesting as an increased mortality rate. Given this, there is every chance that a half-way decent first generation rejuvenation therapy would be of some benefit to people at age 40, those the medical establishment currently designates as being in perfect health, but who nonetheless have a mortality rate that is considerably higher than is the case for people at age 20.
I have a pill. If you decide to take my pill, you immediately stop aging and are preserved in your current physical state from this day forward. This hypothetical pill that stops aging, call it the Methuselah pill, will not make you immortal. Immortality does not exist in this world. Whether or not you age, you can still step in front of a bus, eat a contaminated hamburger, catch a stray bullet, or be struck by lightning. In fact, if you lived long enough one of these things would almost be guaranteed to happen to you.
One way that scientists define aging is that it increases the chance that you will die in the coming year. In America, your chance of dying doubles every 8 years after about age 35. But with the Methuselah pill that no longer happens. You have the same chance of dying, you look the same, you feel the same, as the age at which you took the pill, forever. Would you want to be frozen in time with the physical looks, the energy, strength and agility you had when you were 20? Give this some careful thought because half of you - the male half - may remember 20 as the testosterone-soaked age at which you were more than a little crazy. Maybe you'd like to be preserved at age 50, when people will take you more seriously. You would be more settled in life, a bit more thoughtful, a bit less swift.
One thing to consider. The age you choose to stop aging has a great deal to do with how much longer you can expect to live. A little simple algebra with U.S. government statistics shows that with a 20 year old male survival rate lasting into infinity, your life expectancy is another 600 years rather than the 57 years it is in reality. Not a bad bargain for staying a little crazy. If you're a woman, you're not so crazy at that age and you are also better designed for survival than your male counterparts. That's a sad fact of biology, men. You could expect to survive another 1700 years rather than 62 years you can expect in reality, nearly three times as long as those crazy men. I know it doesn't sound fair, fellows, but age 20 is when the survival advantage of women over men is close to its greatest.
If you decided to stop aging when you are a dignified and mature 50 year-old, you will have sacrificed a lot of future years to achieve that dignified look. Fifty year olds are about 6 times more likely to die in a given year than 20 year olds. Not only that, but you could expect to live with some aches and pains that you didn't anticipate. You won't hear as well and will probably be holding the newspaper or your smart phone at arm's length, but at least that testosterone problem will no longer be so pressing. Your life expectancy, however, has dropped to a mere 140 years if you're a man and a little over 200 years if you're a woman. Ladies, that decision to stop aging at 50 rather than 20 has cost you 1500 years of life expectancy and a considerable amount of pain. You suspected it was a bad decision, didn't you?
The point of this exercise, I suppose, besides having a little fun and stimulating a little thought is to give readers a visceral feel for the toll that aging exacts on us. Back here in the real world, there has been only one confirmed 120 year old person, a woman naturally, in the history of our species. No one yet has approached even 130 years, although some of us researchers are working to change that.