4 ms·

Whether cancer is special in this regard depends on what you mean by aging. I work in this area and consider it to mean "damage (maladaptive changes) that accum

by cgiles 8y ago

Whether cancer is special in this regard depends on what you mean by aging. I work in this area and consider it to mean "damage (maladaptive changes) that accumulate over time, first degrading function and ultimately leading to catastrophic failure" . This is not the only model but it is widespread. So for something like the cardiovascular system, chronic stress, inflammation, ROS etc are the triggers, atherosclerosis and endothelial weakening is the damage, and stroke or heart attack is the failure. In the case of cancer, it is radiation or replication error, DNA mutation, and metastasis, respectively. The key for "curing" aging would be the ability to reverse or repair damage (in this case, to selectively kill cells that are mutated or precancerous). To extend life it is sufficient to merely slow damage accumulation rate.

YeGoblynQueenne 8y ago
I don't claim to understand how all this stuff works, besides the part about modelling it as a probability (a Bernoulli process), but I wonder to what extent it is possible to slow the damage. For instance, if you're bleeding, you may be able to slow it - but if you don't stop it completely, eventually you will bleed to death. I also wonder whether someone living for a very long time wouldn't eventually suffer irreparable damage because of the radiation from the environment accumulating in the tissues. Nobody's claiming that we can survive, say, being thrown into a volcano (an active one, I mean), just by being more healthy and young. There are clearly environmental hazards that the body cannot withstand, senescence or no senescence. It is very likely that such environmental hazards hitherto unforseen will begin to reveal themselves once our lives are extended enough and that we will eventually find out that there is a hard upper limit for the amount of time that these frail bodies can keep serving for. I clarify that this is not something to celebrate, or even accept. Let us not go gentle in to that good night, by all means. On the other hand I think it is ridiculous to believe that in a universe where galaxies die, human beings can keep going like the Duracell bunny for as long as we like, thanks to Nick Bostrom's Amazing Rejuvenating Pills™.
- cgiles 8y ago
  > I wonder to what extent it is possible to slow the damage. For instance, if you're bleeding, you may be able to slow it - but if you don't stop it completely, eventually you will bleed to death. Yes, exactly. Well, the simplistic model is that you have a rate of damage (RD) and rate of repair/replacement (RP), and if RD > RP, the system will eventually fall apart. "Repair" consists of both your body's endogeneous repair or replacement processes and exogeneous things we might do. Most researchers focus on RD, because it seems easier for us to do things about that. Calorie restriction probably mostly affects RD instead of RP, for example. In high theory, one could stop aging purely by lowering RD enough so that it is below the body's endogeneous RR. But in reality, it is easier for the body to detect and repair some kinds of damage than others. It is quite hard for the body to detect DNA mutation in a cell before it starts actively causing aberrant behavior in a cell, although such mechanisms exist. > I think it is ridiculous to believe that in a universe where galaxies die, human beings can keep going like the Duracell bunny for as long as we like Well, at THAT timescale, we are talking about problems of physics and thermodynamics, not biology. But if you consider that in some sense life on Earth has proceeded in an unbroken chain for ~4B years, you can see that it is possible to go quite far by decreasing local entropy at the expense, of course, of global entropy. I do not see how physics prevents human lifespan of at least 10K years, but the technical problems are immense, and I do not predict major success within our lifetimes.

by cgiles 8y ago

YeGoblynQueenne 8y ago

I don't claim to understand how all this stuff works, besides the part about modelling it as a probability (a Bernoulli process), but I wonder to what extent it is possible to slow the damage. For instance, if you're bleeding, you may be able to slow it - but if you don't stop it completely, eventually you will bleed to death. I also wonder whether someone living for a very long time wouldn't eventually suffer irreparable damage because of the radiation from the environment accumulating in the tissues. Nobody's claiming that we can survive, say, being thrown into a volcano (an active one, I mean), just by being more healthy and young. There are clearly environmental hazards that the body cannot withstand, senescence or no senescence. It is very likely that such environmental hazards hitherto unforseen will begin to reveal themselves once our lives are extended enough and that we will eventually find out that there is a hard upper limit for the amount of time that these frail bodies can keep serving for. I clarify that this is not something to celebrate, or even accept. Let us not go gentle in to that good night, by all means. On the other hand I think it is ridiculous to believe that in a universe where galaxies die, human beings can keep going like the Duracell bunny for as long as we like, thanks to Nick Bostrom's Amazing Rejuvenating Pills™.

cgiles 8y ago
> I wonder to what extent it is possible to slow the damage. For instance, if you're bleeding, you may be able to slow it - but if you don't stop it completely, eventually you will bleed to death. Yes, exactly. Well, the simplistic model is that you have a rate of damage (RD) and rate of repair/replacement (RP), and if RD > RP, the system will eventually fall apart. "Repair" consists of both your body's endogeneous repair or replacement processes and exogeneous things we might do. Most researchers focus on RD, because it seems easier for us to do things about that. Calorie restriction probably mostly affects RD instead of RP, for example. In high theory, one could stop aging purely by lowering RD enough so that it is below the body's endogeneous RR. But in reality, it is easier for the body to detect and repair some kinds of damage than others. It is quite hard for the body to detect DNA mutation in a cell before it starts actively causing aberrant behavior in a cell, although such mechanisms exist. > I think it is ridiculous to believe that in a universe where galaxies die, human beings can keep going like the Duracell bunny for as long as we like Well, at THAT timescale, we are talking about problems of physics and thermodynamics, not biology. But if you consider that in some sense life on Earth has proceeded in an unbroken chain for ~4B years, you can see that it is possible to go quite far by decreasing local entropy at the expense, of course, of global entropy. I do not see how physics prevents human lifespan of at least 10K years, but the technical problems are immense, and I do not predict major success within our lifetimes.