Lifespan and Causes of Death in the Irish Wolfhound - Vetsuisse ...

veterinary lifespan studies goes beyond the scope of this thesis. For more
information on the topic, consult Urfer (2007, in prep)
7.1.3 Differences in Previous Studies' Results
When comparing lifespan calculated from the data of the previously published
studies, highly significant differences can be observed between the North American
(Bernardi 1986; Prokopenko 1998) and the Anglo-Irish dogs (Murphy 1991), the latter
living on average 1.4 years longer than their North American counterparts.
There are several potential interpretations of these differences. Obviously, it is
possible that Irish Wolfhounds in Ireland and Great Britain have a higher life
expectancy than Irish Wolfhounds in North America. Although the populations are
genetically close (see chapter 6.3), the relative isolation due to quarantine laws that
existed in Ireland ant the UK during the study period may have favoured different
developments in this population. The importance of country class in the General
Linear Model used for the author's data may also be indicative of this hypothesis.
The distribution of birth cohorts in the two datasets varies: While Bernardi's and
Prokopenko's data only contain 6.27% of dogs born before 1965, Murphy (1991)
contains 14.04% of such dogs. Since it could be shown in the present study that Irish
Wolfhounds lived longer in the 1960s than they did later on, this may also have had
an influence on these differences.
It is also possible that Murphy (1991) was more influenced by submitter's bias (see
chapter 3.1.1.1) than were Bernardi (1986) and Prokopenko (1998): The former drew
its data almost exclusively from breeders, who may have been more motivated to
submit older dogs than to submit those that died young. On the other hand, the North
American studies also included data contributed by important numbers pet owners,
who may have had fewer interests in promoting a particular kennel or family.
These same demographics could also have contributed to the measured lifespan
through another mechanism: It could be assumed that people running a breeding
kennel may be more educated in veterinary medicine than the average dog owner,
which may lead to an increase in life expectancy in their dogs.
7.1.4 Gender and Castration Effects
The data used in this study unanimously suggest that female Irish Wolfhounds on
average have a longer lifespan than do males (chapters 5.1.5, 5.2.1.3 and 6.2.4).
While little data have been published about gender effects on lifespan in dogs, this
mirrors the situation in humans. It is possible that the shorter life expectancy in males
may also be mediated through their larger size to a certain extent.
A gender predisposition of male Irish Wolfhounds to Dilatative Cardiomyopathy has
been described in numerous studies (see chapter 3.3.2) and was also reproduced in
the study at hand (see chapters 5.1.5 and 6.2.4), thus further supporting the
hypothesis that a sex predisposition for this disease exists in the breed.
The predisposition of female Irish Wolfhounds to death by cancers other than
Osteosarcoma has not been described in the literature beforehand. However, the
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