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Link Between Birth Month and Canine Heart Disease Risk
For both dogs and people, it seems that in utero exposure to air pollutants may increase the risk for cardiovascular disease development later in life.
Research conducted at the University of Pennsylvania Perelman School of Medicine and published earlier this year revealed that first-trimester exposure to outdoor air pollution—which peaks during certain months of the year—increases a person’s risk for atrial fibrillation later in life.
Now, new research from the same university shows that birth season incurs the same risk for dogs; those born from June through August are at higher risk of developing heart disease than those born in other months, potentially as a result of exposure to fine air particulates that are at peak levels during the summer months.
Given the physiologic similarities between the human and canine cardiovascular systems, this finding did not come as a surprise to the investigators.
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“Humans and dogs share their lives together and are exposed to similar environmental effects,” said Mary Regina Boland, PhD, assistant professor of informatics in biostatistics and epidemiology at the University of Pennsylvania’s Perelman School of Medicine and lead author of both studies, “so seeing this birth season-cardiovascular disease relationship in both species illuminates mechanisms behind this birth-season disease relationship."
The investigators studied data from the Orthopedic Foundation for Animals (OFA) on 129,778 dogs encompassing 253 different breeds to determine the birth month difference in heart disease risk among predisposed and non-predisposed dogs.
Breeds that are genetically predisposed to heart disease (golden retrievers, dachshunds, miniature and toy poodles, Doberman pinschers, boxers, cavalier King Charles spaniels) did not show a significant change in outcome based on birth month. But breeds not genetically predisposed (Norfolk terriers, Berger Picards, American Staffordshire terriers, English toy spaniels, Bouvier des Flandres, Border terriers, Havaneses) were shown to be at higher risk.
This is important, the investigators noted, “because it suggests that birth month is more informative [than genetic predisposition] on whether a dog will develop cardiovascular disease among purebred dogs in the OFA.”
Depending on breed, dogs have an overall 0.3% to 2% risk of heart disease. The study results showed that dogs born between June and August had an increased risk of developing cardiovascular disease. For dogs not predisposed to heart disease, peak risk occurred in July (74% higher risk), and for dogs predisposed to heart disease, peak risk occurred in September.
While there is some overlap, these peak months differ from those identified in the human study—between January and April. “This suggests the possibility that the cardiovascular disease risk exposure may be closer to conception than previously thought,” the researchers wrote.
These findings indicate that acquired cardiovascular disease in dogs, especially those not genetically predisposed to cardiovascular disease, is birth season dependent. But there is still much more work to be done to explore the types of outside air pollution exposure and how they affect canine and human hearts during development. Future studies, the investigators stated, can help elucidate causal mechanisms underlying the birth season—cardiovascular disease relationship.