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Name: Alex
Status: student
Grade: N/A
Location: MO
Country: N/A
Date: 4/11/2005

What EXACTLY causes "death by natural causes"? Obviously, aging counts into this, but how does aging kill people? I am interested to know: just what are these "natural causes"? Does cancer count as a "natural cause"; what about heart disease?

I don't think I can say "exactly" what it means. "Natural causes" is not a scientific term; it's more of a legal categorization. It will mean about what the locals' feel it means, according to their common sense.

Let's work through our own categories: Murder by an intelligent creature is not a "natural cause". Animal attacks, probably not. Inanimate accidents and natural disasters, also not, even though volcano eruptions are natural phenomena. Micro-organism attacks? Known rare deadies are not, but if it's common in the environment and average humans could fight it off, but you couldn't because of your age, maybe it would be considered natural causes. Certainly long-term malfunctioning body subsystems are the heart of the idea.

Death has been modeled as an exponential increase in the rate of illnesses with age. Even with no micro-organisms attacking, the body is not well enough designed to function indefinitely. Something always breaks down eventually. What breakdowns, how many, and when they happen, is randomly distributed among individuals, except for conformance to average delays which may have been sculpted by evolution. Some of those functions our medicine can't re-establish or substitute for, and some of those are neccessary for life.

Whether it could be otherwise, is thus far a mystery of reality that leads into engineering philosophy, evolution theory, religious beliefs, and stories like "Babylon 5". I wouldn't knock any of them.

Specifically, yes, cancer and heart disease count as natural causes. Notice that neither of them clearly requires any external cause, although some are thought to exist. What else could I add? Certainly strokes. Maybe Alzheimer's. Many degenerative diseases causing relatively early deaths stand out as probable genetic defects. Osteoporosis should be included, in principle, but in practice it's fatalities always feature an accident and complications in the hospital, both of which might be said to clutter our perception of the cause. Decreasing immune function and healing rates figure prominently. Combine three of them in one case, and to which do you attribute the death? "Natural causes".

I guess external vs. internal origin is one defining theme. Admittedly we can't always know which accurately.

Jim Swenson

Hello Alex!

Well, death by natural causes is basically saying that all people die. Cancer would be considered a natural cause, as would heart failure, etc. Long time ago, before everything that happened to someone medically had to be defined and every question answered, when an older individual died and they didn't know the mechanism behind their death (usually sudden deaths, or death in sleep), it was said they died of natural causes.

As for age and death, one of the biggest factors actually has to do with cell replication. Most of our cells are not meant to live forever --> we are meant to die! Your cells divide and divide and divide and their daughter cells do the same, so one and such forth. With every cell division, DNA from one cell is replicated for the next. At the ends of these DNA strands there are sequences called Telomeres. For most of the cells in our body, with each replication these telomere sequence gets shorter. Understand, the telomere sequence has no purpose, other than to protect the important part of DNA from being cut off from these shortenings. It is thought that one of the reasons we age is that these telomeres get too short, or disappear entirely simply by the cell of an older individual being a product of thousands, if not millions, of divisions.

There are also many other reasons for aging, including inactivation of genes that make important proteins, DNA mutations, and effects that hormones and other naturally occuring drugs have on our bodies.

I hope that helps to answer your question. Really, the question you have asked is a very good one and the answer is far more complicated than most of us realize, and the answer is not fully understood!

Best Wishes

Susannah Sample, BSBME
Veterinary Medical Student

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