Washington: Dogs - the best friend humans have got - make for the best companions. Their human friends don't mind going to lengths to ensure their health and well-being.
Hence, attention to all dog-owners and lovers, dogs born in wintertime are healthier.
According to a study conducted by the University of Pennsylvania School of Medicine, dogs born in June through August are at higher risk of heart disease than those born in other months, rising in July to 74 percent higher risk. A correlation to outdoor air pollution may be the culprit.
The birth month difference in risk was marginal among breeds that are genetically predisposed to the disease, suggesting that heart disease acquired later in life may be birth season dependent among all dog breeds.
Breeds not genetically predisposed to cardiovascular diseases, such as Norfolk terrier, Berger Picard, American Staffordshire terrier, English toy spaniel, Bouvier des Flandres, Border terrier, and Havanese were found to be at highest risk.
Also, breeds born frequently in July - Norfolk terrier and Berger Picard - were at increased heart disease risk.
Overall, dogs have a 0.3 to 2 percent risk of developing heart disease depending on breed. The research team found that risk climbs to the greatest level in dogs born in July, that have a 74 percent greater risk of heart disease than would typically be expected.
"It's important to study dogs because the canine heart is a remarkably similar model to the human cardiovascular system," said researcher Mary Regina Boland. "Also, humans and dogs share their lives together and are exposed to similar environmental effects, so seeing this birth season-cardiovascular disease relationship in both species illuminates mechanisms behind this birth-season disease relationship."
The Penn team studied data from the Orthopaedic Foundation of Animals on 129,778 canines encompassing 253 different breeds.
Since the significant association between birth season and cardiovascular disease was found in dogs that are not genetically predisposed to the condition, the authors say the effect supports an environmental mechanism.
This period between June through August is also a peak period for exposure to fine air particulates - such as those produced by factory pollution.
For both dogs and humans, outside air pollution during pregnancy and at the time of birth appears to play a role in later development of heart disease.
In the prior study, the team investigated data from 10.5 million patients from around the world. One of their key findings was a link between first-trimester exposure to fine air particulates and nine percent increased the risk of the heart rhythm irregularity known as atrial fibrillation (Afib) later in life.
People exposed to peak air pollution during the first trimester of their mother's pregnancy were found to be at a nine percent higher risk than usual.
Taken together, the two study findings lead the authors to suggest that pollution is a possible mechanism for the increased risk.
Since dogs' pregnancies are shorter than humans (lasting only 2 months), the proposed mechanism is still thought to be through the mother's inhalation of air pollution affecting the uterine environment, which in turn affects the developing cardiovascular system of the baby or puppy.
The study appears in the journal Scientific Reports.