By Dr. Karen Shaw Becker
Cats are cute, cuddly and undeniably quirky, but recent research suggests having one in your home could be good for health too, particularly when it comes to asthma. What's more, they offer this benefit by changing the activation of your genes! A variation of the gene 17q21, called TT, is the strongest known genetic risk factor for childhood asthma.
Researchers from the Copenhagen Studies on Asthma in Childhood Research Center (COPSAC), Denmark studied 377 children whose mothers had asthma, about one-third of whom also carried the TT gene variant.1
When activated, the TT gene variant doubles asthma risk and is also linked to bronchitis and pneumonia.2 However, when children had a cat in their home, the gene was not activated and they had a much lower risk of developing asthma. The risk of pneumonia and bronchitis was also reduced in children living in cat-containing households. Dogs did not have the same asthma-reducing effects as cats, however.
It's an intriguing study that shows a person's environment, including whether or not it contains certain pets, can influence genetics in a way that promotes or prevents disease. Study co-author Dr. Hans Bisgaard said in a news release, "[The study] documents the interplay between genetics and the environment we live in, and in particular that this occurs very early in life, both during pregnancy and in the home."3
Are Babies Raised Around Pets Healthier?
This isn't the first time pets have been singled out as a harbinger of health. In 2015, a U.K. study of more than 4,700 children found cat ownership was associated with a reduced risk of wheezing during childhood (asthma is a common cause of recurrent wheezing).4 In addition, children exposed to higher levels of cat allergens in household dust during their first three years of life had a lower risk of developing asthma by age 7.5
The researchers believe exposure to "a broad variety of indoor allergens, bacteria, and bacterial products early in life may reduce the risk of developing asthma."6 Indeed, dogs have also been found to have protective effects. For instance, a study of nearly 400 children revealed that babies exposed to dogs during their first year of life had fewer symptoms of respiratory infections and ear infections, and tended to need fewer courses of antibiotics.7
Research presented at the American College of Allergy, Asthma and Immunology (ACAAI) 2017 Scientific Meeting further revealed that exposure to dog "elements" such as bacteria may have a protective effect against asthma symptoms. Another study presented at the meeting found mothers exposed to dogs during pregnancy had children with a significantly lower risk of eczema by age 2 (although the protection seemed to decrease by age 10).8
There has long been debate over whether pets exacerbate allergic disease or help it, but the accumulating evidence seems to point to the latter. The American Academy of Allergy Asthma & Immunology notes:9
"The relationship between early life exposure to animals and the development of allergies and asthma is somewhat confusing and there are many factors to consider. Previous evidence suggested that children exposed to animals early in life are more likely to develop allergies and asthma.
More recent research seems to show that early exposure to animals (cats and dogs in particular) may actually protect children from developing these diseases. Newer research also suggests children raised on farms develop fewer allergies and asthma."
Exposure to both dogs and farm animals during the first year of life reduces the risk of asthma in children at age 6,10 and exposure to farms in early childhood also reduces children's risk of severe respiratory illnesses.11
Why Might Exposure to Pets Be Protective?
As for why spending time around pets like cats and dogs may lower your risk of allergies and asthma, there are likely many factors at play. As the featured study revealed, a genetic component may be involved. Arne Høst of the University of Southern Denmark, who was not involved in the study, told Science Nordic:12
"It's very exciting that they find this connection because other studies have struggled to conclude anything final … Now it looks like the effect is linked to a particular gene-variant, which goes to show just how complex the development of asthma and allergies are. It's not only about genes and the environment, but how the two interact, and there's so much that we still don't know."
The featured study researchers suggested cats may have a protective effect via the bacteria they carry or even fungi or viruses that they bring into the home. It's been shown, for instance, that exposure to pets while in the womb or up to 3 months of age increased the levels of two strains of gut bacteria.13 One is Ruminococcus, which is linked to a reduction in childhood allergies. The other is Oscillospira, which is linked to a lower risk of childhood obesity.
The levels of these two bacteria were twice as high in babies with exposure to a pet in the home. The route of exposure is indirect, from dog to mother to baby during pregnancy as well as the first 3 months of life.
Anita Kozyrskyj, Ph.D., study co-author, University of Alberta pediatric epidemiologist and a leading researcher on gut microbes, told Science Daily, "There's definitely a critical window of time when gut immunity and microbes co-develop and when disruptions to the process result in changes to gut immunity."14
While you probably don't look at the furry pet in your home as another way to expose you (and your children) to a potentially beneficial and diverse array of microbes, he very much is, and evidence is mounting that early exposure to pets primes infants' immune systems to learn the difference between harmful pathogens and harmless environmental irritants, perhaps leading to lifelong benefits.