Pet Forum / Mammals / Rats / October 2005

RAT LONGEVITY (revised/reposted)

Under unnatural circumstances & with special medications & supplements the
oldest rat in the Long-Evans database lived 61 months -- in a group of
experiments designed to prolong life with not even ONE additional rat
making it so long as that. Out of hundreds & hundreds reported from
controlled longevity studies. We're not talking a healthy happy 61 months
either, we're talking last-legs pathetic.

In a study done at Semmelweis University of Medicine in Budapest [reported
in Mech Ageing Dev, December 1988] the average lifespan of rats treated
with the longevity drug deprenyl was just under 37 months, with ONE rat
out of 66 living to the fantastic old age of 57 months. Control study rats
not given the longevity drug lived 47 months at maximum, most were dead in
less than 32. By this study, we can see that IF you provided special
longevity drugs to your rats, even then less than two in a hundred of them
would reach the age of four. The majority would make it only one month
beyond the age of 3, which is the normal lifespan of healthy rats, so even
longevity drugs provide only that extra 4 weeks benefit to the majority.

A study in which rats were fed 40% of the amount of food required to keep
them active, supplemented with chromium picolinate, it was found their
lifespan could be extended to 4 years & rarer still nearly five for the
occasional animal. The trade-off is that they spent this lengthened life
in a state of what microbiologist Ann Storey called "suspended animation"
with no mental or physical stimulation or capacity to reproduce. When the
study was first reported in 1994 by M. F. McCarty, it was widely reported
among rat fanciers & discussed at length if rat care should include
chromium picolinate supplements & starvation in order to increase rats'
lifespan to the occasional animal living a bit under five years as a
nearly inert pet. The universal outcome of these discussions was that a
life without motion or environmental interaction was not much of a life, &
achieving the normal three-year life with a hard-grain no-fat diet would
be great enough, & most of us can't even manage that when our ratties love
& beg for life-shortening treats like bread & sunflower seeds & yogurt.
 (See McCarthy "Longevity Effect of Chromium Picolinate" in MEDICAL
HYPOTHESES 43, 1994.)

The Long-Evans Rat Longevity Database showed that one rat in ten, with
cromium supplements & near-starvation, lived just under 49 months, with an
average of 44 months for the group of ten. The "average" is most important
because it was the highest of any study group -- in other groups the
occasional animal lived four years but the majority never more than three,
so the chromium study was of unusual interest for extending the average.
What it showed was that if rats were kept on a starvation diet so that
they rarely moved & received chromium supplements to counteract the
unhealthful effects of this inertia, their lives could be extended on
average to 3.6 years & in one out of ten cases to a little over 4 years.
No other control group had averages that high. The oldest rat in the
Database was 61 months in a group that lived on average less than 39, &
the second oldest in the data base lived just under 51 months in a group
that for the majority lived only 27 months -- in each group these were
disease-free rats kept under identical circumstances of shared lineage. In
each group there was found the OCCASIONAL animal that would live into its
fourth year with the majority dying by age three.

Healthy longevity to age three was found to be more likely in rats who
took the opportunity of VOLUNTARY exercise akin to that provided by
putting them in wire cages that do permit incidental but persistent
climbing exercise, or for rats that frequently use running wheels (as alas
only a small percentage of pet rats do because unlike mice & gerbils, rats
have to learn to use a wheel, usually from mother rats who already know
how). Any environment that does not permit a rat voluntary & incidental
exercise lowers their age average to well under three years, while those
who voluntarily exercise will live just over three years in a better state
of health. See for example: "Effect of Voluntary Exercise on Longevity of
Rats" by Holloszy et al, in THE JOURNAL OF APPLIED PHYSIOLOGY 59, 1985. In
a glass box with little opportunity for incidental & voluntary climbing
exercise, shortened lifespan averages are inevitable.

Rats that receive adequate exercise & eat primarily whole grains & no
fatty foods & no junkfood & which do not contract lung infections or
tumors or viruses, are apt to live to age three then stroke out from the
natural biological clock that is the same in all rats everywhere in the
world. Without intervention less than two in a hundred will reach a fourth
year naturally, & with heroic interventions that average can be raised to
one in ten living into their fourth year but at considerable detriment to
quality of that life. Rats "spoiled" on treats or living in aquariums
where adequate excercize & ventillation are not a possibility, they'll be
lucky if they reach age three with the last full year being one of misery
& sickness. Exceptions wouldn't be surprising. See "Life Term Studies in
Rats" in THE JOURNAL OF NUTRITION 105, 1975.

I am old enough to remember when rats rarely experienced tumors, & elderly
rats rarely experienced lung infections. In those good old days rats made
it to age three without illness, though the oldest would lose weight, &
eventually stroke out for a rapid death to conclude a healthy life. For a
number of reasons, pet rats today are just about universally afflicted by
immune stresses (lifelong subclinical myco, numerous viruses, poor
breeding for color varieties rather than for longevity or health, mediocre
to poor diets). Where 25 to 40 years ago stroke in old age took most pet
rats, today it will most commonly be either lung disease or tumors, the
result of immunosuppression.

-paghat the ratgirl