Chapter 18 Rehabilitation for Geriatric Patients 455Defining and identifying the geriatric
patient: chronology and size
The 2012 Demographic Survey of US Pet
Ownership reported that 33.2% of the canine
population was aged 6–10 years old (up from
29.8% reported in 2006) and 14.7% was aged 11
years and older (up from 14.1% reported in 2006)
(AVMA, 2012). Extrapolating from Table 18.1,
between 14.7% and 47.9% of the pet population
is moving into the second half of their life span.
Understanding aging is important so that adjust
ments can be made to accommodate for physio
logical changes that occur in older patients.
According to the Senior Care Guidelines Task
Force of the American Animal Hospital
Association (AAHA, 2005), dogs are considered
senior (geriatric) when they are in the last 25% of
their breed’s life expectancy. Clients have easy
access to many sources of aging tables, so it is
important for the rehabilitation therapist to be
well versed on current information about aging
(PetPlace, 2015). It is generally accepted that
smaller breeds of dogs have a longer life span
and are considered geriatric at an older age than
larger breeds of dogs. While not listing specific
breeds, the information in Table 18.1 is a gener
ally accepted guideline reference for determining
when dogs of different breed sizes may be con
sidered geriatric, although a life expectancy
study of 299,555 dogs insured in Japan (Inoue
et al., 2015) indicated that dogs weighing less
than 5 kg had a slightly shorter life expectancy
than dogs in the 5‐10 kg group. Note that in this
study, in contrast to previously reported canine
longevity studies, the category of dog breeds
weighing less than 10 kg was further divided into
toy breeds (body weight <5 kg) and small breeds
(5–10 kg). The authors indicate that further
research is needed to identify why toy breeds
had a shorter life expectancy than small breeds.
The Inoue study provided the following sub
categories of life expectancy according to body‐
weight: 13.8 years for <5 kg, 14.2 years for
5–10 kg, 13.6 years for 10–20 kg, 12.5 years for
20–40 kg, and 10.6 years for the >40 kg group
(Inoue et al., 2015). If one applies the calculation
for determining when a dog is considered geri
atric (in the last 25% of their life expectancy),
the geriatric ages are as follows: 10.35 years for
<5 kg, 10.65 years for 5–10 kg, 10.2 years for
10–20 kg, 9.375 years for 20–40 kg, and 7.95 years
for dogs in the >40 kg group.
There are many factors that are being stud
ied to identify relationships between breed size
and life span. Since there are considerably
more factors to the aging process than chronol
ogy, a working knowledge of the various phys
iological changes that occur is critical to
providing appropriate rehabilitation therapy.
Senescence (from the Latin, senescere, which
means to grow old) can refer to individual cel
lular aging and deterioration, aging, deteriora
tion, and decreased function of individual
organ systems, or aging of the entire organism.
Mechanisms by which to change the rate of
senescence is a topic of much discussion and
research. One study seemed to show that
senescence begins at an earlier age in giant
breeds (>50 kg) than in smaller dog breeds.
Once senescence begins, aging progresses more
rapidly (Kraus et al., 2013).
According to Cornelia Kraus, an evolution
ary biologist at the University of Gottingen in
Germany, a review of data from more than
56,000 dogs including 74 different breeds
showed that dogs lose about 1 month of life
expectancy for each increase of 4.4 pounds
(2.0 kg) (Kraus et al., 2013). Differences in insu
lin‐like growth factor 1 (IGF‐1) between breed
groups has been reported as a factor in growth,
aging, and senescence (Sutter, et al., 2007; Kraus
et al., 2013; Inoue et al., 2015). A study by Fick
et al. (2012) revealed peripheral blood mononu
clear cell (PBMC) telomere length to be a statis
tically significant (p <0.0001) predictor of
average life span among 15 breeds tested, indi
cating that telomeres play a role in determining
the average canine life span. This study may
also reveal information as to why our canine
companions live a shorter overall life than peo
ple: dogs lose telomeric DNA approximately
10‐fold faster than humans, which is similar toTable 18.1 Ages at which dogs may be considered
geriatric
Dog size Body weight Age (mean ± SD)Small 0–10^ kg (0–20 lbs) 11.48 ± 1.86
Medium 10–20 kg (21–50 lbs) 10.19 ± 1.56
Large 20–40 kg (51–90 lbs) 8.85 ± 1.38
Giant >40 kg (>90 lbs) 7.46 ± 1.27Source: Adapted from Goldston (1995)