From: sbharris@ix.netcom.com(Steven B. Harris) Subject: Re: In Defence of the Unofficial Live Doctor's Club (if people suddenly became as healthy as their pets) Date: 22 Nov 1996 Newsgroups: misc.health.alternative In <19961122164500.LAA03133@ladder01.news.aol.com> davidharel@aol.com writes: >So preach no more pig Doctor, of your mineral fountain of youth! >Our patients clearly do not need this, even if it is the truth. >Can't you see how many jobs would go? You human Vet! >If people suddenly became as healthy as their pets. David Harrell must have never owned a pet which lived to near the end of its maximum lifespan. Pets do (routinely) get grey and arthritic. They get infections and abscesses, heart failure and diabetes. You don't see an awful lot of this because most people's pets are young-- without really good medical care, cats and dogs generally don't live to be more than about 10 or 12 (equivalent in human terms to about 50, no matter what you hear about the ratio of 7:1).* Usually they don't make it that long. And when they do get blind, or get arthritis, hip dysplasia or heart problems, they get taken to the vet for that special piece of vetrinary medical care which you'd probably disapprove of if we doctors suggested it routinely for chronically ill people. How many of those people Wallace autopsied had been put down? As for farm animals, don't make me laugh. In age, most farm animals are the equivalents of highschool kids. Even so, they occasionally get sick, as any practising vet will tell you. Geez, didn't you ever read any James Heriot books? Steve Harris, M.D. * If you want to calculate the true physiologic "human age-equivalent" of your dog, the first two years bring the animal to the human equivalent of 15, and every year after that is about 4 in human terms. From: sbharris@ix.netcom.com(Steven B. Harris) Newsgroups: misc.fitness.weights,sci.med Subject: Re: Harris shows off his pop view of dogs! Date: 11 Sep 1998 08:29:20 GMT In <35F83BD6.C8E4315D@tico.com> John Wash <j_wash@tico.com> writes: John Wash <j_wash@tico.com> in Message-ID: <35F83BD6.C8E4315D@tico.com> states: >>Congratulations, you've just demonstrated your utter unfamiliarity with the subject at hand.<< Rather the opposite. But you had to put your foot in it, didn't you? >> Perhaps you looked up the life expectancy of Deerhounds on the AKC web site, or maybe you even have a copy of The Dog Book (which is notorious for overstating the good traits of most breeds).< No, I looked up on one of many Scottish deerhound websites, at www.deerhound.org/growth.htm. I can only assume that if Scottish deerhound affictionados don't know how long the animals live, no one does. Not, not even you. >> The popular "seven years" concept has been pretty much refuted.<< That's nice, because I did not assume it. Stop putting words in my mouth. My comments about equivalent ages were based on Pfizer canine life tables, and the veterinary literature. >> It is not a linear progression. << I never said it was. Though who knows what you mean by a linear progression. In a way, *after* maturity, there is a proportional increase in mortality with time, between organisms. This is a little difficult to put into words without the math (Gompertz exponent factors are constant and proportional; each species has a characteristic exponential rate constant). But basically it means that after maturity a year of aging for one species or breed of animal is equivalent to x number of years for another--- and that for the remainder of life into old age, this ratio does not change. >> For example, in general, smaller breeds mature much faster (at least in terms of reaching adult size) than larger breeds.<< Correct. Aging, at least as defined in terms of risk of mortality beginning to increase in an exponential fashion, does not begin until puberty and most of growth. In dogs that happens at roughly a year for small breeds, at which time they are about equivalent to humans at 15. Large breeds are about at human age 12, and just entering the fastest development. By two years (equivalent to age 24 for small breeds, 19 for larger ones), growth is complete. Such comparisons are made by looking at tooth maturity, bone epiphyseal closure, etc. After maturity, however, the Gompertz law takes over, and, mortality risk doubles every 7 years in humans, and about every 1 to 2 years in dogs, depending on breed. If you want a ratio between dogs and humans for mortality doubling time it would, I suppose, be anywhere from 4 to 7 years to 1, provided you *start* at dog age 2 = human age 19-24. Maximum life span for reasonably large populations of dogs (and cats also) is about 20 years. This corresponds to about 100 for humans (neither of these is world record, but what you'd expect to be the max for a small town). Life expectancies (again) would imply a human/canine ratio of as low as 4 in doubling time for mortality for the longest lived breeds (eg, poodles), and as much as 11 for the shortest lived breeds. >>Which means that, using your math and your multiplier, smaller breeds have a life expectancy equivalent of 105 years, hmm? << You never saw my math, and you have no idea (or didn't until 10 seconds ago) what a proper multiplier for this might be, or how one might use it. Obviously, not all breeds have the same one, and growth isn't complete at the same time in all breeds, as you note. That just means you start at a different place, when comparing people to dogs. Again, however, *after* maturity, a reasonable mortality "doubling rate" multiplier as compared with humans might be 4-5 for smaller breeds, and on the order of 10 or more for the very large ones. (Many medium sized breeds, such as labrador retrievers, have excellent life expectancies, however. As do standard poodles). Of course, smaller breeds don't always outlive larger ones-- it's only a tendency. A breed by breed analysis is necessary, and has only been attempted in a few places. Still, if you want some tables of very roughly equivalent ages between humans and dogs of different size, you can see them at http://www.pfizer.com/ah/level2/petown/dogown/k9au.html These folks study dogs for a living. You don't. The Pfizer tables, btw, use a mortality rate multiplier of 4 from small breeds and 7 for large ones, after maturity. These figures are averaged from life tables. But the multiplier is than 7 for the largest breeds. >>Look, there's just no good way to match up average human and average dog life expectancy. There is such a huge variation amongst breeds that any attempt to do it for the entire species is doomed to failure.<< I never tried to do it for the entire species. But there is a range in dog breed life expectancy from roughly 7 to 13, which corresponds with maximum life spans of roughly 10 to 20. The very large breeds don't usually last more than 10 years, so it's quite easy to compare that with age 70 or 80 in humans (always remembering to use populations of humans getting no better medical care than the average pet). The characteristic exponential rise in mortality with age after full growth (or puberty) is a feature of aging in nearly all iteroparous organisms, and it's just a matter of constructing the life tables and finding out what it is. That's been done for dogs in some of the references below. I recommend them. >>Any time you want to go head-to-head with me on the subject of dogs, little man, you just give a shout.<< Hey, don't look now, but that's what we've been doing. You seem to know nothing about the aging of dogs or any other creature. You're not familiar with either the geriatric literature or the even the websites. All you have is your little dead dog stories. Fine. Tell them. Regarding the Roberts vitamin C fiasco: >>You didn't prove anything. Bill wasn't wrong.<< "Wrong" is probably too kind. His answer was meaningless, and did not indicate that he understood the first thing about what he was saying. "No more than a few hours" is supposed to apply to what? "Vitamin C in the body" (what was asked about) does not have "a" half life. Different fractions of it have greatly differing half lives. Nobody asked "What's the half life of the fraction of the megadose of vitamin C I just took that I'm going to dump fast into my urine, until my body gets down to normal levels?" The answer to that, if it was even answerable, might be: "That can vary from one hour to 10 hours or more, depending on how big a megadose you took and how well your kidneys work-- assuming you were completely repleted to begin with." But all that's way too complicated for the conversation that actually took place. "No more than a few hours" is flat out wrong if it's supposed to apply to everybody's megadose clearance. Also, this entire exchange totally ignores my other point, which is that on one hand we have Bill saying he doesn't really know the answer to a question, but he's going to give an estimate anyway. That's something he says nobody ever does in misc.health.fitness. Well, actually, you do. And when you do, being human, you screw up. The problem is that you don't really want to admit to being human. You all think you're some kind of transformer toys. I haven't seen so much adolescent posturing since I quit reading comic books. A LONG time ago. Steve Harris, M.D. Eur J Med Res 1998 Feb 21;3(1-2):31-41 Geriatrics in canine and feline internal medicine. Berl Munch Tierarztl Wochenschr 1996 Aug;109(8):292-303 [Life expectancy and cause of death in dogs. I. The situation in mixed breeds and various dog breeds]. [Article in German] Bottom line: life expectancy from a low of 6.8 years in the Berner Sennenhund (that's St. Bernard to you, Wash) to 13.0 years for the Pudel (even you can figure that one out). Mixed breeds did no better than purebreds. Vet Rec 1997 Jul 12;141(2):40-44 Mortality in insured Swedish dogs: rates and causes of death in various breeds. Data on over 222,000 Swedish dogs of various breeds (250 of them), which got good care because they were enrolled in pet care insurance programs (a third of Swedish dogs). The place to go for the best stats. |