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The Worst Birth Month for Future Health Problems

canine heart disease

Story at-a-glance -

  • A recent study suggests that for dogs with no genetic predisposition to cardiovascular disease, being born during the summer months increases the risk for heart problems later in life
  • June through August is considered a peak period for outdoor air pollution, and researchers theorize there is a link between fine air particulates and acquired canine heart disease
  • Dogs born in July have a 74 percent greater risk for heart disease than average
  • Signs of a potential heart problem in dogs include coughing, exercise intolerance, respiratory distress, behavior changes and fainting or collapsing
  • There are many things dog parents can do to proactively protect their pet’s heart health

By Dr. Karen Shaw Becker

I have some news to report about dogs and heart disease that’s a little disturbing. A recently published study by researchers at the University of Pennsylvania’s Perelman School of Medicine suggests that dogs born in the months of June, July and August are at higher risk of heart disease than those born during other months of the year, and there seems to be a correlation with outdoor air pollution.1

These findings suggest there are potential environmental factors involved that also affect long-term outcomes for humans born during the warmer months of the year.2

"It's important to study dogs because the canine heart is a remarkably similar model to the human cardiovascular system," said lead study author Mary Regina Boland, Ph.D., an assistant professor of informatics in biostatistics and epidemiology

"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."3

While I feel compelled to share this information, I don’t think there’s any reason to lay awake at night worrying about it. Number one, many of us have no idea what month our rescues were born, and even if you bought your puppy from a breeder, they can’t always regulate the month their litters will be born. More importantly, there are many things you can do to help prevent, delay and/or effectively manage heart disease in your canine companion.

Study Results Show Dogs Born in July Are at Highest Risk

For their study, the Penn researchers looked at data on nearly 130,000 dogs across over 250 breeds. They concluded that for breeds genetically predisposed to heart disease, birth month risk was minimal. This suggests heart disease that develops later in life may be influenced by birth season across all breeds. Certain breeds with no genetic predisposition to heart problems were at highest risk, including:

Norfolk Terrier

Bouvier des Flandres

Berger Picard

Border Terrier

American Staffordshire Terrier


English Toy Spaniel

All dogs have a 0.3 to 2 percent risk of developing heart disease, depending on breed. The Penn researchers found that dogs born in July have a 74 percent greater risk of heart disease than average.

Summer Months Are a Peak Period for Air Pollution

Because the link between birth month and heart disease is seen in breeds without a genetic predisposition, the researchers believe there’s an environmental component at work. And indeed, the months of June through August are considered a peak period for the presence of fine air particulates (e.g., factory pollution).

Another recently published study of 10.5 million human patients from across the globe reported a link between exposure to fine air particulates during the first trimester and increased risk of atrial fibrillation (a heart rhythm abnormality) later in life. Babies exposed to peak air pollution during their first trimester were at a 9 percent higher risk than normal.4

The results of the two studies led the Penn researchers to conclude that pollution is a possible contributor. Since dog pregnancies are only 2 months versus 9 months for humans, they theorize that the mother’s inhalation of air pollution influences the environment in the uterus, which in turn affects the still developing cardiovascular system of the baby or puppy. It’s important to note, however, that other known contributors to heart disease, such as diet and exercise, were not evaluated.

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Most Canine Cardiovascular Disease Is Acquired

Heart disease in canines can be congenital (hereditary), but the vast majority of cases (95 percent) are acquired. It is typically a condition of middle-aged and older dogs, and involves either the heart muscle itself, or the valves of the heart.
Common heart disorders in dogs include:

  • Valvular disease: Heart valve problems are the most common type of canine heart disease. The valves of the heart weaken with age and begin to leak when the heart muscle pumps.
  • Heartworm disease: Mosquitoes are the carriers. The worms take up residence in the heart and cause disease.
  • Myocarditis: This condition is characterized by inflammation of the heart caused by infection (usually bacterial). Myocarditis both weakens and enlarges the heart muscle.
  • Pericardial disease: The protective sac around a dog's heart fills with liquid, interfering with the normal beating mechanism.
  • Arrhythmia: Arrhythmia is an irregular heartbeat brought on by a problem with the body's electrical control system.

Interestingly, one of the most common reasons for heart disease in humans, blocked arteries, is rare in dogs. However, in my experience, both dogs and humans do share one significant risk factor: diet. For dogs, it’s the biologically inappropriate, highly processed diet many are fed throughout their lives.

Signs That Can Signal a Problem With Your Dog’s Heart

Coughing: A recent, persistent cough that is worse at night, or when your pet has been laying down, or stands up from a sitting or reclining position is one of the more obvious signs of a potential issue with the heart.

Exercise intolerance: If your dog seems to be moving around less and is reluctant to play or exercise, it’s a red flag. She may begin to wear out after just a short exercise session, and you may notice she’s breathing heavier after exertion. Another sign is purplish or pale gums.

Respiratory distress: Pets with a heart problem often have an increased respiration rate during sleep. A normal respiration rate is under 32 breaths per minute, and you can check your dog’s rate by counting the rises or falls of his chest for one minute. If he’s taking more than 32 breaths per minute or you notice there is an abdominal effort to breathe, it may indicate a heart problem.

Behavior changes: Look for increased or generalized restlessness, especially at night, as though she can’t decide where to lie down.

Fainting or collapsing: If heart disease is severe or advanced, dogs may faint or collapse. This is clearly a sign of a very serious medical emergency and your pet needs to see a veterinarian right away.

Weight fluctuations: Dogs with long-term heart disease typically experience weight loss, but weight gain is also possible as a result of fluid accumulation in the abdomen. Look for a bloated or pot belly.

5 Tips to Proactively Protect Your Dog's Heart Health

  • Ask your veterinarian for the proBNP blood test. This test can give you peace of mind that your dog has no early signs of heart disease. It's a simple blood test with a fast turnaround time that can provide the information you need to proactively manage your dog's heart health.
  • If you have a breed genetically predisposed to heart issues, consider a screening test that identifies the issue early, so you can do something about it. I recommend all dogs genetically predisposed to any type of heart problem begin ubiquinol as puppies and continue this supplement throughout their lives.
  • Help your dog maintain a good body weight through regular aerobic exercise.
  • Feed a high-quality (human-grade), nutritionally balanced and species-appropriate diet that meets your dog's nutritional requirements for optimal protein (and amino acid) levels, healthy fat, EFAs (essential fatty acids, e.g., omega-3s) and coenzyme Q10, as well as critical micronutrients such as vitamins D and E, calcium, zinc and magnesium, which are often deficient in homemade, unbalanced diets.
  • Take excellent care of your dog's dental health (bacteria from dirty mouths have been linked to heart valve infections in dogs).