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A Dog's Birth Month May Predict Its Cardiovascular Health

Being born in the summer may be risky for your dog's heart.

SC Psychological Enterprises Ltd.
Source: SC Psychological Enterprises Ltd.

This article is not about astrology, where a birth date is associated with positions of the planets and the stars, and the influence of these astronomical bodies is supposed to affect your destiny. However, science has found that your birth month, or at least which season you are born in, might affect aspects of your life including your health, and perhaps even certain behavioral tendencies. A new report suggests that birth date might not only affect people, but also may have an influence on dogs and their physical health.

Over the past few years, several studies have shown that if you are born early in the year (between January and March) you are at the highest susceptibility for a variety of heart related difficulties. We can contrast this to those who are born in September or October who have the lowest rate of heart problems. Dogs, overall, tend to be much less susceptible to heart diseases than humans; however their cardiovascular system is similar enough to people so that dogs have traditionally been used in research on various medical procedures for heart problems. For example, the first angiograms and the first pacemakers were tested on laboratory dogs. Given the similarity between humans and canines, a team of researchers headed by Mary Regina Boland from the Perelman School of Medicine at the University of Pennsylvania in Philadelphia, decided to see if a dog's birthday was associated with its heart health in ways that are similar to those found in people and this research just recently appeared in the journal Science Reports.

The first problem they encountered was finding a data source that would give them a large block of information on the health of dogs. For this they eventually turned to the Orthopedic Foundation of Animals (OFA), which is a nonprofit organization based in Columbia, Missouri. It has the largest fully searchable online canine health database in the world. From this database, the research team was able to gather records from 129,778 dogs, representing 253 distinct breeds, who had had at least one heart examination registered with the OFA.

Once the data was in hand, the researchers recognized that they had to deal with the complication that some dog breeds are noted for being genetically predisposed to cardiovascular disease. For example, all Cavalier King Charles Spaniels are considered to have at least Class A cardiovascular disease even if no heart murmur is present. If there are seasonal birth effects they might have different impacts on dogs with a pre-existing predisposition toward a weak heart. So the team divided the data into those breeds prone to heart problems and those that had a low incidence of these.

It turns out that their statistical analysis showed a definite association between a dog's birth month and the likelihood of heart disease. The largest effects of birth date on heart problems turns out to be in the dog breeds that are not known to have inherited susceptibilities to cardiovascular problems. The risk for this group was highest in the summer months running from June through August. The analysis showed that the dogs born at the peak month for susceptibility (in July) had a likelihood of heart disease that was nearly twice the risk seen in dogs born in the month showing the lowest hazard rate (May). The effect was not as strong for those breeds that have a congenital risk of heart problems, and the pattern for this group was displaced slightly later in the year. For the group known to have a higher likelihood for cardiovascular problems, the highest jeopardy was for dogs born in September and the lowest was for dogs born in June. The results for this group was still large and significant with the difference between the peak risk birth dates and the safest birth dates amounting to an approximate 50% in relative jeapordy.

The fact that birth date has a large impact on heart problems in dog breeds that usually are at lower risk suggests that something associated with the environment might be involved. Dogs which are born in July were probably conceived sometime around May. This is a time when the particulate matter in the air is increasing to its maximum, at least in the northern hemisphere. Particulate densities rise in the spring due to the presence of high levels of pollen from flowers and grass, and there is also often more dust in the air due to drier weather conditions as the summer approaches. If we flash back to the human data it turns out that the people born in the months that are most closely associated with higher rates of heart disease were also conceived sometime around May. So the researchers speculate that it is this stuff in the air which may affect responses of the immune system during the early stages of pregnancy, and the chemical and hormonal responses that result may be causing later heart problems in both humans and dogs. This, however, is merely a hypothesis and the investigators cautiously suggest that the reason for these seasonal effects must still be considered to be unknown.

I was having coffee with some acquaintances and mentioned that I had just read this paper which showed that a dog's birthday could predict its susceptibility to heart problems when one of the people in the group chimed in, "I'll bet worst months for heart disease in the dogs are July and August."

I looked at her quizzically and said, "You are generally correct in your assumption, but what makes you say that?"

She replied, "Well the astrological sign of Leo goes from July through August and Leo is ruled by the Sun which has influence over the heart and cardiovascular system and…"

As I said at the beginning of this article, it's really not about astrology, or at least those of us who are scientists believe that it's not about astrology.


Mary Regina Boland, Marc S. Kraus, Eddie Dziuk & Anna R. Gelzer (2018).Cardiovascular Disease Risk Varies by Birth Month in Canines. Scientific Reports, doi:10.1038/s41598-018-25199-w

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