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Estimating the life expectancy of companion dogs in Japan using pet cemetery data

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The life expectancy provides valuable information about population health. The life expectancies were evaluated in 12,039 dogs which were buried or cremated during January 2012 to March 2015. The data of dogs were collected at the eight animal cemeteries in Tokyo. The overall life expectancy of dogs was 13.7 (95% confidence interval (CI): 13.7-13.8) years. The probability of death was high in the first year of life, lowest in the fourth year, and increased exponentially after four years of age like Gompertz curve in semilog graph. The life expectancy of companion dogs in Tokyo has increased 1.67 fold from 8.6 years to 13.7 years over the past three decades. Canine crossbreed life expectancy (15.1 years, 95% CI 14.9-15.3) was significantly greater than pure breed life expectancy (13.6 years, 95%CI 13.5-13.7, P-value <0.001). The life expectancy for male and for female dogs were 13.6 (95% CI: 13.5-13.7) and 13.5 (95% CI: 13.4-13.6) years, respectively, with no significant difference (P=0.097). In terms of the median age of death and life expectancy for major breeds, Shiba had the highest median age of death (15.7 years), life expectancy (15.5 years) and French Bulldog had the lowest median age of death (10.2 years), life expectancy (10.2 years). When considering life expectancy alone, these results suggest that the health of companion dogs in Japan has significantly improved over the past 30 years.
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*Correspondence to: Inoue, M.: kuro_felis_catus@me.com
©2018 The Japanese Society of Veterinary Science
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FULL PAPER
Internal Medicine
Estimating the life expectancy of companion
dogs in Japan using pet cemetery data
Mai INOUE1)*, Nigel C. L. KWAN1) and Katsuaki SUGIURA1)
1)Department of Global Agricultural Sciences, Graduate School of Agricultural and Life Sciences, The University
of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
ABSTRACT. The life expectancy provides valuable information about population health. The
life expectancies were evaluated in 12,039 dogs which were buried or cremated during January
2012 to March 2015. The data of dogs were collected at the eight animal cemeteries in Tokyo.
The overall life expectancy of dogs was 13.7 (95% condence interval (CI): 13.7–13.8) years. The
probability of death was high in the rst year of life, lowest in the fourth year, and increased
exponentially after four years of age like Gompertz curve in semilog graph. The life expectancy of
companion dogs in Tokyo has increased 1.67 fold from 8.6 years to 13.7 years over the past three
decades. Canine crossbreed life expectancy (15.1 years, 95% CI 14.9–15.3) was signicantly greater
than pure breed life expectancy (13.6 years, 95%CI 13.5–13.7, P-value <0.001). The life expectancy
for male and for female dogs were 13.6 (95% CI: 13.5–13.7) and 13.5 (95% CI: 13.4–13.6) years,
respectively, with no signicant dierence (P=0.097). In terms of the median age of death and
life expectancy for major breeds, Shiba had the highest median age of death (15.7 years), life
expectancy (15.5 years) and French Bulldog had the lowest median age of death (10.2 years), life
expectancy (10.2 years). When considering life expectancy alone, these results suggest that the
health of companion dogs in Japan has signicantly improved over the past 30 years.
KEY WORDS: dog, Japan, life expectancy, pet cemetery data
Dogs are the most popular companion animal in Japan with a population estimated to be 9.9 million in October 2016, and with
14.2% of households owning one or more dogs as companion animals [9]. An increasing number of dogs in Japan apparently enjoy
improved health than hitherto partly due to the use of commercial pet food and partly to veterinary medical care [11]. As a result,
their life expectancy is expected to have been extended in recent years.
The estimate of life expectancy provides valuable information about the health and nutritional status of companion animals in a
specic group. Although there have been many studies estimating the longevity of dogs, most of these studies used the median age
as indicator of longevity [14, 16], due to the sample sizes used not being large enough to construct a life table. A relatively large
sample of dying dogs is needed to construct a life table, reecting the ages of all dying individual dogs, and thereby to estimate
the average life expectancy by age, sex and breed. Life table is dened as a valuable analytical tool to summarize the mortality
experience of the current population and to study longevity [1].
There are two principal forms of the life table: the cohort (or generation) life table and the current life table. The cohort life table
records the actual mortality experience of a particular group of individuals (the cohort) over its entire lifetime. The current life
table gives a cross-sectional view of the mortality and survival experience of a population during a current year and is dependent
on the age-specic death rates prevailing in the year for which it is constructed [1].
Previously, Hayashidani et al. [6] conducted a study to estimate the life expectancy of dogs in Japan using pet cemetery data
from 1981 to 1982, constructed a cohort life table and estimated the life expectancy of dogs to be 8.3 years at birth (age zero)
and 8.6 years at one year old (age one). Inoue et al. [7] constructed a current life table for insured dogs from 2010 to 2011 and
estimated their life expectancy to be 13.7 years at birth. The results of these studies were not comparable because of the dierent
types of life table and data source. The data based on the cemeteries was biased in the region (only in Tokyo) and the data based on
the insurance was biased in age, breed, urban/rural areas and accessibility to medical care.
The purpose of this study was to estimate the life expectancy of companion dogs in Japan by constructing a cohort life table and
median, minimum and maximum age at death using data collected at animal cemeteries in Tokyo, and to compare the longevity
with previous study in Japan. We also calculated the proportional mortality by month and season.
Received: 11 July 2017
Accepted: 14 May 2018
Published online in J-STAGE:
24 May 2018
J. Vet. Med. Sci.
80(7): 1153 –115 8, 2018
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M. INOUE ET AL.
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MATERIALS AND METHODS
Data collection
Data on 12,039 dogs which were buried or cremated during January 2012 to March 2015 were collected at the eight animal
cemeteries which were members of the Tokyo Society of Pet Cemeteries (under the auspice of Tokyo Metropolitan Veterinary
Medical Association). Information on the dog’s sex, breed, age (in years and in months) and month of death were collected by face-
to-face interview with the owner or the person who brought the dog to the cemetery using a standardized questionnaire. Data was
not available on whether or not the dogs were naturally deceased or euthanised. In cases where the owner or the person was unable
to remember the dog’s exact age in months and only able to remember the age rounded down in years, a random number between 0
and 11 was generated and added to the age stated to compute the dog’s age in months (n=4,230).
Construction of life table
We assumed that the 12,039 dogs included in the current study as a cohort and constructed a cohort life table using the method
described in Chiang [1]. In constructing the life table, we used an age interval of one year (x, x+1). The basic variables involved
in a cohort life table are lx, the number living at age x and dx, the number dying in the age interval (x, x+1). We calculated the
probability of a dog dying in age interval (x, x+1), as a proportion of dogs that died during this age interval over the dogs alive
at age x. . We calculated the fraction of last year of life for age x, áx as the average of the fraction of last year of life for
dogs that had died during the interval (x, x+1). We calculated the number of years lived by the total cohort in interval (x, x+1),
Lx = (lxdx)+ax×dx. We calculated total number of years lived beyond age x, Tx as the sum of the number of years lived in each
age interval beginning with age x. Tx = Lx + Lx+1 + ··· + Lw, x =0, 1, …, w. We constructed a life table using these vaiables, in
accordance with the method described by Chiang [1]. The life expectancy at age was calculated, as the number of years, on the
average, yet to be lived by a dog of age x. . We constructed a life table for all breeds and sexes combined and for pure and
cross breeds and for dierent sexes. We calculated the variance (S) and standard error (S.E.) of life expectancy using the method
described by Chiang [1]. The signicance of dierence (di) of life expectancy between dierent breed groups and sexes was also
tested. The statistics for Z test was calculated by , where and were life expectancy at age 0 of dierent
breed and sexes groups, and S.E. (di.) was dened as (Chiang, 1984). The threshold of
signicance was P-value=0.05. The 95% condence intervals were calculated by .
We also calculated the life expectancy at age 0 for 21 dog breeds whose sample size (n) was larger than 100, as well as their
median, minimum and maximum age of death.
Proportional mortality by month and season
The proportional mortality by month was calculated as a proportion of dogs that died in the respective months over the total
number of dogs that died. Likewise, the proportional mortality by season was calculated as a proportion of dogs that died in the
respective seasons (summer: April to September; winter: October to March). The dierences were tested using χ2 test for a single
comparison. The 95% condence intervals were calculated using the formula
95 196%CI.ˆp
ˆp (1ˆp )
N
where is the extimated
proportion and n is the sample size for the respective months or seasons.
For all statistical analyses, Excel 14.0 (Microsoft Corporation) was utilized.
RESULTS
Table 1 shows the cohort life table for all breeds and sexes combined. The probability of death was 0.0099 in the rst year of
life, and decreased to its lowest in the fourth year of life, and increased like a Gompertz curve after four years old in semilog graph
(Fig. 1). The life expectancy at age zero, or the average lifespan was 13.7 (95% Condence Interval (CI): 13.7–13.8) years. The
cross breed had a signicantly longer life expectancy (15.1 years, 95% CI: 14.9–15.3) than pure breed (13.6 years, 95%CI:13.5–
13.7) (z-test, P-value <0.001, Table 2). The life expectancy for male and for female dogs was 13.6 (95%CI:13.5–13.7) and 13.5
(95%CI: 13.4–13.6) years, respectively, with no signicant dierence (z-test, P-value=0.097, Table 2).
The median age of death was 14.0 years for all breeds and sexes combined. Shiba had the highest expectation of life at age 0
(15.5 years) and median age of death (15.7 years), and French Bulldog had the lowest expectation of life at age 0 (10.2 years) and
median age of death (10.2 years) (Table 3).
In terms of the month of death, 10.3% of the dogs that died in this study died in February, 7.2% of the dogs died in June, 11.1%
of dogs in December (Fig. 2). The proportion of dogs that died in the winter season (October to March) was higher than that of
dogs that died in summer season (April to September) with signicant dierence (χ2, P<0.05).
EXTENDED LIFE EXPECTANCY OF DOGS IN JAPAN
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DISCUSSION
We constructed a cohort life table using animal cemetery records in Tokyo, aiming to provide scientic information on the
average life expectancy of companion dogs in Japan. The average number of registered companion dogs in Tokyo in 2012–2015
under the Rabies Prevention Law was 516,750 [15]. The sample size of the dogs subjected to the current study represented 2.3%
(=12,039/516,750) of the registered companion dog population in Tokyo. To examine how much we can generalize from our data,
we compared the dog population brought to the cemeteries with the general dog population in Japan. We examined if the dog
population used in our study is representative of the general dog population in terms of breed. According to the result of a survey
conducted by the Japan Pet Food Association in 2015, cross breed dogs represent 17.5% of the dog population in Japan [9], while
the cross breed dogs represented 9.3% of the dog population used in our study. This indicates that the pure breed dogs might be
over-represented in our study, and consequently the overall life expectancy might have been underestimated.
In our study, we estimated an overall life expectancy of 13.7 at age zero, while a previous study by Hayashidani et al. [6]
estimated an overall life expectancy of 8.3 and 8.6 years at ages zero and one respectively, by constructing a cohort life table
using data of 4,915 dogs brought to a cemetery in Tokyo. Their results showed that the life expectancy at age zero (8.3 years) was
lower than that at age one (8.6 years) with the probability of death at age zero (0.15), being higher than that at age one (0.06).
This phenomenon, which was not observed in our study, might be attributed to sampling bias as a result of owners’ behavior who
seldom buried their dogs at young ages in those years [6]. Moreover, in their study the probability of death at the ages 10, 15
and 20 was relatively high, indicating that the owners most probably rounded up and down the dogs ages as they got older [6].
Despite these dierences in data quality and presence of biases in our and their studies, the life expectancy of companion dogs in
Tokyo has increased 1.67 fold from 8.6 years to 13.7 years over the past three decades. The leading causes of death for companion
dogs in the early 1980s were infectious diseases such as heartworm disease, gastrointestinal nematodiasis and canine distemper,
hit-by-car accident and malnutrition [18]. The increased provision of veterinary care and the assumed improved nutrition as a
result of increasing use of well-balanced commercial pet food as well as promotion of animal welfare among Japanese people in
recent years might have resulted in the extended life expectancy in recent years. In the other study in the UK, the median estimate
of 11.1 years from dogs insured and attending dog shows in 1999 [14], the median longevity for dogs of 12.0 years from primary
veterinary hospital data in 2013 has reported [16]. These studies showed the longevity of dogs has extended considerably in these
countries.
Table 1. Cohort life table for companion dogs for all breeds and sexes combined
Age interval
in years
Probability of
dying in interval
(x,x+1)
Number
living at
age x
Number dying
in interval
(x,x+1)
Fraction of
last year of
life
Number of years
lived in interval
(x,x+1)
Total number
of years lived
beyond age x
Expectation
of life at
age x 95% Condence
Interval of êx
x to x+1 lxdxáxLxTxêx
0–1 0.0099 12,039 119 0.3 11,953 165,225 13.7 13.7 13.8
1–2 0.0083 11,920 99 0.6 11,876 153,272 12.9 12.8 – 12.9
2–3 0.0066 11,821 78 0.4 11,775 141,396 12.0 11.9 – 12.0
3–4 0.0062 11,743 73 0.5 11,706 129,620 11.0 11.0 – 11.1
4–5 0.0059 11,670 69 0.5 11,633 117,914 10.1 10.0 – 10.2
5–6 0.0092 11,601 107 0.5 11,548 106,281 9.2 9.1 9.2
6–7 0.0124 11,494 143 0.4 11,412 94,732 8.2 8.2 8.3
7–8 0.0157 11,351 178 0.5 11,257 83,320 7.3 7.3 7.4
8–9 0.0286 11,173 319 0.5 11,006 72,063 6.4 6.4 6.5
9–10 0.0404 10,854 438 0.5 10,617 61,057 5.6 5.6 5.7
10–11 0.0611 10,416 636 0.4 10,058 50,440 4.8 4.8 4.9
11–12 0.0818 9,780 800 0.5 9,347 40,382 4.1 4.1 4.2
12–13 0.1219 8,980 1,095 0.5 8,390 31,035 3.5 3.4 3.5
13–14 0.1612 7,885 1,271 0.4 7,184 22,644 2.9 2.8 2.9
14–15 0.2292 6,614 1,516 0.5 5,797 15,461 2.3 2.3 2.4
15–16 0.3166 5,098 1,614 0.5 4,249 9,664 1.9 1.9 – 1.9
16–17 0.4038 3,484 1,407 0.5 2,732 5,415 1.6 1.5 – 1.6
17–18 0.4872 2,077 1,012 0.5 1,545 2,683 1.3 1.3 – 1.3
18–19 0.6225 1,065 663 0.5 724 1,137 1.1 1.0 1.1
19–20 0.6741 402 271 0.5 272 414 1.0 0.9 1.1
20–21 0.6336 131 83 0.6 94 141 1.1 0.9 1.2
21–22 0.7292 48 35 0.5 29 47 1.0 0.7 1.2
22–23 0.5385 13 7 0.9 12 18 1.4 1.0 1.8
23–24 0.5000 6 3 0.2 4 6 1.0 0.4 1.5
24–25 0.6667 3 2 0.5 2 2 0.8 0.4 1.2
25 1.0000 1 1 0.3 0 0 0.3 0 0.8
q
x
ˆ
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The comparison the life expectancy of common breeds was not enough only using expectation of life at age 0, because the
number of each breeds were small to construction life table. So the median ages of death ware used to evaluate longevity with
expectation of life at age 0. The result of our study was not consistent with the results of previous studies, which reported that
breeds with smaller body mass have greater longevity [12, 13, 17]. Among the eleven dog breeds which had an older expectation
of life age at 0 than all breeds combined (13.7 years), there were four medium breeds (Shiba, cross breed with body weight >10
kg, Shetland Sheepdog and Beagle), three small breeds (Miniture Dachshund, Shih Tzu and Papillon), three toy breed (Yorkshire
Terrier, maltese and Pomeranian) and one large breed (Labrador Retriever); while among the ten dog breeds which had a younger
expectation of life age at 0, there were one large breed (Golden Retriever), three medium breeds (American Cocker Spaniel,
Pembroke Welsh Corgi and French Bulldog), four small breeds (Miniature Schnauzer, Cavalier King Charles Spaniel, Pug and
cross breed with body weight <10 kg) and two toy breeds (Chihuahua and Toy Poodle) (Table 3). This suggests that the longevity
of dogs might not be directly related to the size of the breed and highlighted the need to analyze life expectancy at individual breed
level since there could be certain common diseases aecting a particular breed.
Fig. 1. Probability of dying of dogs.
Table 2. Life expectancy of companion dogs by breed and sex
Breed/Sex Number Expectation of
life at age 0
(95% Condence
Interval) P-Value
All 12,039 13.7 (13.7 – 13.8)
Breed
Pure Breed 10,922 13.6 (13.5 – 13.7) <0.00001
Cross Breed 1,117 15.1 (14.9 – 15.3)
Sex
Male 6,189 13.6 (13.5 – 13.7) =0.097
Female 5,850 13.5 (13.4 – 13.6)
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In the present study, Shiba had the oldest age of death (15.7 years) which was even higher than that for cross breeds (BW >10
kg) (15.4 years). According to a recent study using data from insured dogs in Japan [8], the prevalence of dermatological disorders
in Shiba was high (mean annual prevalence is 29%), while the prevalence of life threatening diseases such as neoplasia and
cardiovascular disorders were relatively low. Moreover, French Bulldog, Golden Retriever, Pug, Chihuahua and Cavalier King
Charles Spaniel, which had a relatively low life expectancy based on our results, were all breeds with high risk of neoplasia or
cardiovascular disorders [8]. Since dogs appear to display variation in life expectancy and causes of death across individual breeds
[4, 16], further research on the genetic factors aecting longevity at individual breed level is highly needed.
Recently, the biology of ageing and social factors inuencing longevity have been widely researched [3]. The increasing role
of companion dogs as an animal model for researches in geroscience and life extension science has also been highlighted [5]. In
terms of the reason of larger dog breeds living shorter, it has been hypothesized that they expend relatively more energy to growth
due to slow growth rates and this causes additional base damage to cells as a result of increased oxidative stress [10]. Furthermore,
Table 3. Expectation of life at age 0, median, minimum and maximum age at death of the companion dogs subjected to the analysis
Breeds Number Expectation of
life at age 0
95% Condence
Interval of êx
Age at death (years) Group by
body mass a)
Median Minimum Maximum
Miniature Dachshund 1,578 13.9 13.7 –14.0 13.9 0.0 21.6 Small
Chihuahua 1,079 11.8 11.7– 11.9 11.8 0.0 21.7 To y
Shih Tzu 962 15.0 14.8 15.1 14.8 0.1 20.9 Small
Yorkshire Terrier 784 14.3 14.0 14.5 14.5 0.0 20.3 To y
Shiba 614 15.5 15.3 15.8 15.7 0.0 25.2 Medium
Toy Poodle 560 12.7 12.3 –13.2 13.5 0.0 22.4 Toy
Maltese 437 14.3 13.9–14.6 14.5 0.0 22.8 Toy
Pembroke Welsh Corgi 405 13.5 13.3 13.7 13.3 0.5 18.8 Medium
Pomeranian 386 14.0 13.7 14.4 14.3 0.2 20.7 To y
Papillon 382 14.4 14.1 14.7 14.4 0.5 23.0 Small
Cross breed (BW >10 kg) 368 15.3 15.0–15.6 15.4 0.8 23.9 Medium
Labrador Retriever 328 14.1 13.8 –14.3 14.0 0.6 19.2 Large
Golden Retriever 295 13.1 12.8– 13.4 12.9 0.2 18.0 Large
Miniature Schnauzer 286 13.4 12.9–13.8 13.2 0.1 18.3 Small
Cavalier King Charles Spaniel 251 13.1 12.7–13.4 13.0 0.1 18.5 Small
Shetland Sheepdog 239 14.3 13.9 14.6 14.1 0.8 24.1 Medium
Beagle 205 14.8 14.4 15.1 14.5 3.8 20.0 Medium
Pug 193 12.8 12.1 13.4 12.6 0.2 19.0 Small
Cross breed (BW <10 kg) 182 13.3 12.5–14.0 14.5 0.0 21.2 Small
French Bulldog 151 10.2 9.7– 10.7 10.2 0.1 15.9 Medium
American Cocker Spaniel 139 12.8 12.3 13.3 12.8 0.3 17.7 Medium
Total 12,039 13.7 13.7 13.8 14.0 0.0 25.2
a) Breeds were classied into ve groups of breeds according to their ideal body weights: toy (<5 kg), small (5–10 kg), medium (10−20 kg), large (20−40
kg) and giant (≥40 kg). Data on the ideal weight of each breed were obtained from the Japan Kennel Club (2013).
Fig. 2. Proportional mortality of dogs by month.
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a study on the lifespan of dogs using Rottweiler as a model revealed that the mortality rates of neoplasia for long-living dogs
were lower than that for young dogs [2], suggesting that long-living dogs might have genetic resistance against life-threatening
diseases. In addition, it has been proposed that companion dogs might have higher risks of neoplasia due to the potential exposure
of the carcinogen also aecting humans [19]. Overall, researches on the lifespan and ageing of dogs will help promote the health
of companion dogs, thus improving the quality of life of dogs’ owners and also providing important information to benet human
health.
Proportional mortality by month of companion dogs obtained in our study showed that dogs had a higher probability of death
during the winter season than summer season. Further studies are needed to identify the risk factors aecting the seasonal mortality.
The current study analyzed the life expectancy of dogs in Japan but not their causes of death. Therefore, further mortality
analyses on the causes of death for individual dog breeds at dierent age intervals are warranted to provide scientic information
that will enhance the quality and length of life for companion dogs.
ACKNOWLEDGMENTS. We would like to thank Tokyo Society of Pet Cemeteries and the Tokyo Veterinary Medical Association
for providing us with data of companion dogs for this study.
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... In addition, the odds ratio for death obtained from the data [5] was significantly higher in Labrador Retriever and Shiba, as well as aged dogs, and significantly lower in Chihuahuas, indoor dogs and castrated or spayed dogs. They [4] also examined the data from pet cemeteries for the longevity of dogs and found that the overall life expectancy was 13.7 years, a 1.67-fold increase from 8.6 years in the past 30 years. The life expectancy of cross breed dogs (15.1 years) was significantly longer than purebreds (13.6 years), and there was no sex difference (females 13.5 years, males 13.6 years). ...
... The median ages of the dogs were 2 years, 3 years and 10 years old in the Meiji-Taisho, Showa, and Heisei-Reiwa periods, respectively, and those of the cats were 2 years and 10 years, in the Showa and Heisei-Reiwa periods, respectively. One of the reasons was the extended lifespan of pet animals [4] due to the progression of veterinary medicine such as breeding techniques, environmental hygiene, and spread of vaccines. The result on the age of death obtained in the present necropsy study was comparable to those in some reports published in Japan [1 -7] and in some other countries [9,11], which were calculated using data from an insurance company [1], a pet food association [7], animal cemeteries [2,3,4,5], or veterinary hospitals [6]. ...
... One of the reasons was the extended lifespan of pet animals [4] due to the progression of veterinary medicine such as breeding techniques, environmental hygiene, and spread of vaccines. The result on the age of death obtained in the present necropsy study was comparable to those in some reports published in Japan [1 -7] and in some other countries [9,11], which were calculated using data from an insurance company [1], a pet food association [7], animal cemeteries [2,3,4,5], or veterinary hospitals [6]. ...
Article
There is no nationwide necropsy database of animals in Japan, and most of the records are available from the postwar period. To clarify the chronological transition of animal necropsy cases in Tokyo, Japan, the records accumulated in the University of Tokyo from 1902 were investigated. Of necropsy records on paper or electronic from 1902 to 2021 kept at the Laboratory of Veterinary Pathology, the University of Tokyo, totally 3137 cases including 572 in 1903–1914 (the Meiji-Taisho period), 1258 in 1956–1969 (the Showa period) and 1307 in 2006–2020 (the Heisei-Reiwa period), respectively, were examined for species, breed, age and pathological diagnosis. Dogs (44.6%) and horses (34.8%) in the Meiji-Taisho period, dogs (62.9%) and cats (17.3%) in the Showa period, and dogs (46.0%), cats (26.1%) and exotic animals (20.5%) in the Heisei-Reiwa period were the most necropsied animal species. With the passage of time, the number of animal species increased, and the breeds of dogs and cats came to be more various. The median ages of death were 2 years, 3 years and 10 years old in dogs in the Meiji-Taisho, Showa and Heisei-Reiwa periods, respectively, and 2 years and 10 years old in cats in the Showa and Heisei-Reiwa periods, respectively. Viral, bacterial and parasitic infections were decreased, and inversely tumor cases increased due to the prolonged lifespan.
... www.nature.com/scientificreports/ cohort 9,10 . Both types of life tables have their importance. ...
... Despite their usefulness for the management of human populations, life tables are rarely built for companion animals. Two life table studies for dogs were recently conducted in Japan 10,17 ; the first created current life tables for dogs in general, along with estimates for differing sizes, using pet insurance data, whilst the other created a hypothetical cohort life table using pet cemetery data. These life tables have advanced the knowledge of dog life trajectory 18 and have been applied in studies that required information on the life expectancy of dogs of different ages, such as a quantitative risk assessment of the introduction of rabies 19 and the quantification of welfare impact caused by diseases 2 . ...
... The life expectancy at age 0 reported in the current study for dogs under primary veterinary care in the UK in 2016 was 11.23 years (11.19-11.27), 2.47 years shorter than the life expectancy at age 0 (both 13.7 years) in the two life tables of Japanese dogs constructed using pet insurance and pet cemetery data, discussed above 10,17 . Differing data sources for the study populations might partially contribute to this substantial variation. ...
Article
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A life table is a tabulated expression of life expectancy and mortality-related information at specified ages in a given population. This study utilised VetCompass data to develop life tables for the UK companion dog population and broken down by sex, Kennel Club breed group, and common breeds. Among 30,563 dogs that died between 1st January 2016 and 31st July 2020, life expectancy at age 0 was 11.23 [95% confidence interval (CI): 11.19–11.27] years. Female dogs (11.41 years; 95% CI: 11.35–11.47) had a greater life expectancy than males (11.07 years; 95% CI: 11.01–11.13) at age 0. Life tables varied widely between breeds. Jack Russell Terrier (12.72 years; 95% CI: 12.53–12.90) and French Bulldog (4.53 years; 95% CI: 4.14–5.01) had the longest and shortest life expectancy at age 0, respectively. Life tables generated by the current study allow a deeper understanding of the varied life trajectory across many types of dogs and offer novel insights and applications to improve canine health and welfare. The current study helps promote further understanding of life expectancy, which will benefit pet owners and the veterinary profession, along with many other sectors.
... Pet dogs come from a large variety of breeds and therefore show a huge natural genotypic and phenotypic variability, including a wide range of expected lifespan. The life expectancy of dogs, in general, is associated with their average body weight, as smaller dogs tend to live longer [17][18][19][20]. ...
... The 2 age groups were very distinct, with dogs aged 1-4 years in the young group and dogs aged 14-17 years in the old group (Table 1). The wide age gap of 10 years between the age groups is approximately 73% of the overall average dog lifespan [19]. ...
Article
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Dogs may possess a unique translational potential to investigate neural aging and dementia because they are prone to age-related cognitive decline, including an Alzheimer’s disease–like pathological condition. Yet very little is known about the molecular mechanisms underlying canine cognitive decline. The goal of the current study was to explore the transcriptomic differences between young and old dogs’ frontal cortex, which is a brain region often affected by various forms of age-related dementia in humans. RNA isolates from the frontal cortical brain area of 13 pet dogs, which represented 7 different breeds and crossbreds, were analyzed. The dogs were euthanized for medical reasons, and their bodies had been donated by their owners for scientific purposes. The poly(A) tail RNA subfraction of the total transcriptome was targeted in the sequencing analysis. Cluster analyses, differential gene expression analyses, and gene ontology analyses were carried out to assess which genes and genetic regulatory mechanisms were mostly affected by aging. Age was the most prominent factor in the clustering of the animals, indicating the presence of distinct gene expression patterns related to aging in a genetically variable population. A total of 3436 genes were found to be differentially expressed between the age groups, many of which were linked to neural function, immune system, and protein synthesis. These findings are in accordance with previous human brain aging RNA sequencing studies. Some genes were found to behave more similarly to humans than to rodents, further supporting the applicability of dogs in translational aging research.
... Vaccinations, improved environment, and diet, as well as other preventative measures, have led to an increase in the numbers of dogs that reach "old age" (1,2). As such, the majority of morbidities that afflict companion dogs in developed countries are often aging-related (3), and many of these agerelated diseases are chronic and degenerative, reducing dogs' quality of life. ...
Article
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Osteoarthritis (OA) is one of the most prevalent age-related chronic conditions that afflict companion dogs, and multiple joint supplements are available to prevent or treat OA, though the efficacy of these treatments is controversial. While the demographic factors that are associated with OA diagnosis are well established, the factors that are associated with joint supplement use are not as well studied. Using data collected from the Dog Aging Project, we analyzed owner survey responses regarding joint supplement administration and OA diagnosis for 26,951 adult dogs. In this cross-sectional analysis, logistic regression models and odds-ratios (OR) were employed to determine demographic factors of dogs and their owners that were associated with joint supplement administration. Forty percent of adult dogs in our population were given some type of joint supplement. Perhaps not surprisingly, dogs of older age, larger size, and those that were ever overweight were more likely to receive a joint supplement. Younger owner age, urban living, owner education, and feeding commercial dry food were associated with a reduced likelihood of administration of joint supplements to dogs. Interestingly, mixed breed dogs were also less likely to be administered a joint supplement (OR: 0.73). Dogs with a clinical diagnosis of OA were more likely to receive a joint supplement than those without a reported OA diagnosis (OR: 3.82). Neutered dogs were more likely to have a diagnosis of OA, even after controlling for other demographic factors, yet their prevalence of joint supplement administration was the same as intact dogs. Overall, joint supplement use appears to be high in our large population of dogs in the United States. Prospective studies are needed to determine if joint supplements are more commonly administered as a preventative for OA or after an OA clinical diagnosis.
... High early life mortality has been reported among free-ranging puppies from India [52], but as far as we are aware, the life expectancy of stray dogs in India is unknown. Whilst the average life expectancy among companion dogs can be relatively long-for example, it has been reported to be 13.7 years in Japan [53], we expect it to be much shorter in free-roaming dogs. Further studies need to be conducted to understand adult-juvenile dog ratios in the state. ...
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The overpopulation of stray dogs is a serious public health and animal welfare concern in India. Neglected zoonotic diseases such as rabies and echinococcosis are transmitted at the stray–dog human interface, particularly in low to middle-income countries. The current study was designed to estimate the stray dog populations in Punjab to enhance the implementation of animal birth and disease (for example, rabies vaccination) control programs. This is the first systematic estimation of the stray dog population using a recommended method (mark–re-sight) in Punjab, India. The study was conducted from August 2016 to November 2017 in selected villages or wards in Punjab. For the rural areas, 22 sub-districts in each district were randomly selected, then one village from each of the 22 selected sub-districts was selected (by convenience sampling). For urban areas, 3 towns (less than 100,000 human population) and 2 large cities (more than or equal to 100,000 human population) were randomly selected, followed by convenience selection of two wards from each of the 5 selected towns/cities. To estimate the dog population size, we used a modified mark-re-sight procedure and analysed counts using two methods; the Lincoln–Petersen formula with Chapman’s correction, and an application of Good–Turing theory (SuperDuplicates method; estimated per km2 and per 1000 adult humans and were compared between localities (villages vs. towns), dog sex (male vs. female) and age group (young vs. adult) using linear mixed models with district as a random effect. The predicted mean (95% CI) count of the dogs per village or ward were extrapolated to estimate the number of stray dogs in Punjab based on (a) the number of villages and wards in the state; (b) the adult human population of the state and (c) the built-up area of the state. Median stray dog populations per village and per ward using the Lincoln–Petersen formula with Chapman’s correction were estimated to be 33 and 65 dogs, respectively. Higher estimates of 61 per village and 112 per ward are reported using the SuperDuplicates method. The number of males was significantly higher than the number of females and the number of adult dogs was about three times the number of young dogs. Based on different methods, estimates of the mean stray dog population in the state of Punjab ranged from 519,000 to 1,569,000. The current study revealed that there are a substantial number of stray dogs and a high number reside in rural (versus urban) areas in Punjab. The estimated stray dog numbers pose a potential public health hazard in Punjab. This impact requires assessment. The estimated stray dog numbers will help develop a dog population and rabies control program in which information about the logistics required as well as costs of implementing such programmes in Punjab can be incorporated.
Thesis
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This doctoral thesis quantitatively assessed the effectiveness and appropriateness of the current rabies prevention system in Japan through a variety of mathematical tools including import risk analysis, regression analysis, meta-analysis and benefit-cost analysis.
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The prolonged lifespan of companion dogs has resulted in increased behavioural and physical challenges linked to old age. The development of behavioural tests to identify and monitor age‑related differences has begun. However, standardised testing requires validation. The present study aimed to assess external validity, interobserver reliability, and test–retest reliability of an indoor test battery for the rapid assessment of age‑related behavioural differences in dogs. Two experimenters tested young dogs (N = 20, mean age ± SD = 2.7 ± 0.4 years) and old dogs (N = 18, mean age ± SD = 11.8 ± 1.3 years) in the test battery once and then again after two weeks. Our results found external validity for two subtests out of six. On both test occasions, old dogs committed more errors than young dogs in a memory subtest and showed more object avoidance when encountering a novel object. Interobserver reliability and test–retest reliability was high. We conclude that the Memory and Novel object subtests are valid and reliable for monitoring age‑related memory performance and object neophobic differences in dogs.
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While the lifespan advantage of small body size and mixed breed status has been documented repeatedly, evidence for an effect of genetic diversity across dog breeds is equivocal. We hypothesized that this might be due to a strong right-censoring bias in available breed-specific lifespan estimates where early-dying dogs from birth cohorts that have not died off completely at the time of data collection are sampled disproportionately, especially in breeds with rapidly growing populations. We took advantage of data on owner reported lifespan and cause of death from a large public database to quantify the effect of size and genetic diversity (heterozygosity) on mortality patterns across 118 breeds based on more than 40,000 dogs. After documenting and removing the right-censoring bias from the breed-specific lifespan estimates by including only completed birth cohorts in our analyses, we show that small size and genetic diversity are both linked to a significant increase in mean lifespan across breeds. To better understand the proximate mechanisms underlying these patterns, we then investigated two major mortality causes in dogs — the cumulative pathophysiologies of old age and cancer. Old age lifespan, as well as the percentage of old age mortality, decreased with increasing body size and increased with increasing genetic diversity. The lifespan of dogs dying of cancer followed the same patterns, but while large size significantly increased proportional cancer mortality, we could not detect a significant signal for lowered cancer mortality with increasing diversity. Our findings suggest that outcross programs will be beneficial for breed health and longevity. They also emphasize the need for high-quality mortality data for veterinary epidemiology as well as for developing the dog as a translational model for human geroscience.
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Understanding the longevity and causes of death in dogs and cats can provide helpful information in determining health promotion measures. Using the data of 2,133 dogs and cats that died between 1 April 2020 and 31 August 2021 obtained from 40 veterinary clinics that are members of Team HOPE, a cohort life table was created. The average life expectancy was 13.6 years for dogs and 12.3 years for cats. Neoplasia was the most common cause of death in dogs (18.4%), followed by cardiovascular diseases (17.4%) and urinary diseases (15.2%). Causes of death in cats were urinary diseases (29.4%), neoplasia (20.3%), and cardiovascular diseases (11.8%). The average life expectancy for dogs was expected to be extended by 0.6 and 0.5 years when death caused by neoplasia and cardiovascular diseases was removed respectively. Likewise, the average life expectancy for cats was expected to be extended by 1.6 and 1.0 years if death caused by urinary diseases and neoplasia was removed. The findings of this study could be used by pet owners and veterinary clinicians to introduce effective measures and promote the health care of dogs and cats by prioritizing diseases according to the causes of death.
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Vomiting is a major gastrointestinal (GI) sign of chronic enteropathy (CE) in dogs. Previous studies have reported clinical characteristics of dogs with CE, who developed diarrhea with or without vomiting as GI signs. However, to characterize clinical features of dogs with CE appropriately, dogs presenting with vomiting without diarrhea should be included in the analysis. Thus, this study aimed to characterize clinical features and outcomes of dogs that presented with vomiting without diarrhea. Based on their presenting GI signs, we retrospectively classified 66 dogs with CE into “Vomiting”, “Diarrhea”, or “Vomiting and diarrhea” groups and compared clinical and histological characteristics of each group. We found that 18 of the 66 dogs with CE (27%) presented with vomiting without diarrhea as a GI sign. Compared to the other two groups, the Vomiting group was significantly associated with food-responsive enteropathy (FRE), Beagle, lower clinical severity scores, higher plasma albumin levels, and higher histological scores for eosinophils in the duodenal lamina propria according to the univariate analysis. The multivariate analysis revealed that FRE and higher histological scores for eosinophils in the duodenal lamina propria were significant variables in the Vomiting group. Moreover, the survival time was the longest in the Vomiting group among dogs with CE. These findings are of clinical significance as they indicate that presenting with vomiting without diarrhea may not only be helpful in differentiating FRE from the other types of CE, but also in predicting the prognosis.
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Animal life-history traits fall within a limited ecological space, a continuum referred to as a “slow-fast” life-history axis. Differences of life-history traits are thought to result from trade-offs between behavioral and physiological aspects in each species as mediated by the biotic and abiotic environment, as well as genetic mechanisms. Domestic animals tend to show inverse relationships between body size and life span. Dogs are a good example of this, with smaller dogs having higher mass-specific metabolic rates and longer lifespans compared with larger dogs. Thus, dogs provide a unique system to examine physiological consequences of life-history trade-offs. I have collected data from the literature to explore implications of these trade-offs at several levels of physiological organization including whole-animal, organ systems, and cells. Small dogs tend to have longer lifespans, fewer pups per litter, faster and shorter developmental trajectories, and higher mass-specific metabolic rates, and in general, larger metabolically active organs compared with large dogs. From work on isolated primary fibroblast cells and telomeres of dogs, I show that selection for body size may influence the attributes of cells that shape proliferative cellular rates and rates of telomere shortening. The potential links between body size, and cellular oxidative stress in dogs as they age are discussed. Furthermore, small size in dogs has been linked to concentrations of reduced insulin growth factor-1 (IGF-1) levels in plasma, a possible metabolic advantage that may provide higher resistance to oxidative stress, a parameter essential to increases in lifespan.
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Abstract Large body size is one of the best predictors of long life span across species of mammals. In marked contrast, there is considerable evidence that, within species, larger individuals are actually shorter lived. This apparent cost of larger size is especially evident in the domestic dog, where artificial selection has led to breeds that vary in body size by almost two orders of magnitude and in average life expectancy by a factor of two. Survival costs of large size might be paid at different stages of the life cycle: a higher early mortality, an early onset of senescence, an elevated baseline mortality, or an increased rate of aging. After fitting different mortality hazard models to death data from 74 breeds of dogs, we describe the relationship between size and several mortality components. We did not find a clear correlation between body size and the onset of senescence. The baseline hazard is slightly higher in large dogs, but the driving force behind the trade-off between size and life span is apparently a strong positive relationship between size and aging rate. We conclude that large dogs die young mainly because they age quickly.
Chapter
The companion dog is the most phenotypically diverse species on the planet. This enormous variability between breeds extends not only to morphology and behavior but also to longevity and the disorders that affect dogs. There are remarkable overlaps and similarities between the human and canine species. Dogs closely share our human environment, including its many risk factors, and the veterinary infrastructure to manage health in dogs is second only to the medical infrastructure for humans. Distinct breed-based health profiles, along with their well-developed health record system and high overlap with the human environment, make the companion dog an exceptional model to improve understanding of the physiological, social, and economic impacts of the longevity dividend (LD). In this review, we describe what is already known about age-specific patterns of morbidity and mortality in companion dogs, and then explore whether this existing evidence supports the LD. We also discuss some potential limitations to using dogs as models of aging, including the fact that many dogs are euthanized before they have lived out their natural life span. Overall, we conclude that the companion dog offers high potential as a model system that will enable deeper research into the LD than is otherwise possible.
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AgingDogs live an average of 12 years, cats about 15—and they both have much shorter life spans than we do. Why? The question is part of a larger mystery that has stumped scientists for centuries: Just why do some animals live longer than others? Aristotle thought it had something to do with how much moisture an animal contained; modern scientists have suggested everything from metabolic rate to free radicals. Now researchers may finally be homing in on some answers. The findings could shed light on the mysteries of our pets' life spans—as well as our own.
Article
The life expectancies and causes of death were evaluated in 299,555 dogs insured in Japan between 1 April 2010 and 31 March 2011, of which 4169 dogs died during this period. The overall life expectancy of dogs was 13.7 years. The probability of death was high in the first year of life, lowest in the second and third years, and increased exponentially after 3 years of age. The life expectancy was 13.8 years in the <5kg body weight group, 14.2 years in the 5-10kg body weight group, 13.6 years in the 10-20kg body weight group, 12.5 years in the 20-40kg body weight group and 10.6 years in the ≥40kg body weight group. As body weight increases, life expectancy tended to decrease except in the <5kg body weight group. The probability of death increased as dogs got older for most potential causes of death. Neoplasia resulted in the highest probability of death, especially in the large and giant breed groups. Cardiovascular system disorders were the second major cause of death and the toy group had a probability of death significantly higher than the other breed groups at age 12+. Copyright © 2015 Elsevier B.V. All rights reserved.
Article
We calculated the annual prevalence of diseases of 18 diagnostic categories in the insured dog population in Japan, using data from 299,555 dogs insured between April 2010 and March 2011. The prevalence was highest for dermatological disorders (22.6% for females and 23.3% for males), followed by otic diseases (16.4% for females and 17.2% for males) and digestive system disorders (15.7% for females and 16.4% for males). The prevalence of cardiovascular, urinary, neoplasia and endocrine disorders, increased with age; infectious diseases and injuries showed a high prevalence at young ages, and the prevalence of musculoskeletal and respiratory disorders showed a bimodal peak at young and old ages. A large variation in prevalence was observed between breeds for dermatological, otic, digestive, ophthalmological and cardiovascular disorders. Copyright © 2015 Elsevier B.V. All rights reserved.
Article
Improved understanding of longevity represents a significant welfare opportunity for the domestic dog, given its unparalleled morphological diversity. Epidemiological research using electronic patient records (EPRs) collected from primary veterinary practices overcomes many inherent limitations of referral clinic, owner questionnaire and pet insurance data. Clinical health data from 102,609 owned dogs attending first opinion veterinary practices (n=86) in central and southeast England were analysed, focusing on 5095 confirmed deaths. Of deceased dogs with information available, 3961 (77.9%) were purebred, 2386 (47.0%) were female, 2528 (49.8%) were neutered and 1105 (21.7%) were insured. The overall median longevity was 12.0years (IQR 8.9-14.2). The longest-lived breeds were the Miniature poodle, Bearded collie, Border collie and Miniature dachshund, while the shortest-lived were the Dogue de Bordeaux and Great Dane. The most frequently attributed causes of death were neoplastic, musculoskeletal and neurological disorders. The results of multivariable modelling indicated that longevity in crossbred dogs exceeded purebred dogs by 1.2years (95% confidence interval 0.9-1.4; P<0.001) and that increasing bodyweight was negatively correlated with longevity. The current findings highlight major breed differences for longevity and support the concept of hybrid vigour in dogs.
Article
Anecdotal beliefs and limited research suggest variable patterns of mortality in age, size, and breed cohorts of dogs. Detailed knowledge of mortality patterns would facilitate development of tailored health-maintenance practices and contribute to the understanding of the genetic basis of disease. To describe breed-specific causes of death in all instances of canine mortality recorded in the Veterinary Medical Database (VMDB)(a) between 1984 and 2004. We hypothesized that causes of death, categorized by organ system (OS) or pathophysiologic process (PP), would segregate by age, body mass, and breed. 74,556 dogs from the VMDB for which death was the outcome of the recorded hospital visit. Retrospective study. Causes of death from abstracted VMDB medical records were categorized by OS and PP and analyzed by age, breed, and breed-standard mass of dog. Causes of death, categorized by OS or PP, segregated by age, breed, and breed-standard mass. Young dogs died more commonly of gastrointestinal and infectious causes whereas older dogs died of neurologic and neoplastic causes. Increasing age was associated with an increasing risk of death because of cardiovascular, endocrine, and urogenital causes, but not because of hematopoietic or musculoskeletal causes. Dogs of larger breeds died more commonly of musculoskeletal and gastrointestinal causes whereas dogs of smaller breeds died more commonly of endocrine causes. Not all causes of death contribute equally to mortality within age, size, or breed cohorts. Documented patterns now provide multiple targets for clinical research and intervention.