This week, I read a post by Michelle Roberts in BBC News titled Pet dogs 'may help children avoid asthma' and I remembered that in 2001 the Journal of Allergy and Clinical Immunology (JACI) published Systemic review: Exposure to pets and risk of asthma and asthma-like symptoms.
In 2001, Benjamin J. Apelberg, BS, Yutaka Aoki, MS, MHS, and Jouni J. K. Jaakkola, MD, DSc, PhD (authors of the above linked JACI study) concluded:
- Exposure to pets appears to slightly increase the risk of asthma and wheezing in older children.
- A lower risk of wheezing among exposed (compared to unexposed young children) is consistent with a protective function in this age group but could also be explained by a selection bias (avoidance) related to a family history of allergy.
- Clearly, literature on this topic suffers from numerous design flaws. Few studies exist that address selection mechanisms and appropriate exposure-outcome time frames for a given theory.
"The ideal study would consist of a longitudinal design in which disease status and exposure to pets are assessed at multiple time points."
Well, it appears that this newly published JAMA study, Early Exposure to Dogs and Farm Animals and the Risk of Childhood Asthma, bridged the gaps. The data was derived from a nationwide study of Swedish children born between 2001 and 2010 – a total of 1,011,051 children who were born during the 10-year period.
Earlier Results Yielded Contradictory Findings
Does Living With a Dog or Farm Animals Help or Hinder?
It definitely appears that timing is a big factor.
Vegan Feast Catering on flickr / CC-by-2.0Of the over 1 million children born during the study period, exposure to a dog during the first year of life was associated with a decreased risk of asthma in school-aged children.
In fact, the data from about 650,000 children resulted in a 13% decreased risk of developing asthma in later childhood.
Incredibly, exposure to farm animals was associated with a reduced risk of asthma in both preschoolers and school-aged kids.
Preschoolers exposed to farm animals during their first year of life were 31 percent less likely to develop asthma between 1 and 5 years of age (compared to those not exposed to farm animals before the age of one).
And, a whopping 52 percent of school-age kids exposed to farm animals during their first year of life were less likely to have asthma at age 6 than those who had not been exposed to farm animals during their first year of life.
This large study supports the hypothesis that "exposure to dogs and farm animals during the first year of life reduces the risk of asthma in children at age 6 years."
Why Does Early Exposure to Animals Reduce the Asthma Risk?
Researchers are not entirely certain why or how animals help reduce the risk of asthma. Study author and associate professor of Uppsala University in Sweden, Tove Fall told Live Science:
"It might be due to a single factor, or more likely, a combination of several factors related to a dog ownership lifestyle or dog-owners' attitudes, such as kids' exposure to household dirt and pet dust, time spent outdoors or being physically active. As a parent in a dog-and-baby-household, it is nearly impossible to keep everything clean, and maybe this is a good thing for your baby's future health."
Dr. Fall added:
"My take-home message from this study is that parents at this point do not need to worry about keeping their dog or getting a puppy when expecting a baby for fear of asthmatic disease."
And I was relieved that she stressed:
"I do want to be clear that this recommendation is valid only for families without a child already having allergies. If they already have a furred-animal-allergic child, we do not recommend them to get a furred pet."
In The Globe and Mail, Lisa Rapaport reported that Dr. Tove confirmed by email:
"To let children have a pet in their home is likely to enrich the family life in many ways, and perhaps also enriches the child’s microbiome and immune system."
And an allergy researcher at the University of Washington and Seattle Children’s Hospital, Dr. Frank Virant, suggested that "children who spend a lot of time around dogs or farm animals might be exposed to bacteria that are linked to a lower risk of asthma."
What About Early Exposure to Cats?
julie corsi on flickr / CC-by-2.0In May 2008, ScienceDaily reported that Columbia Center for Children's Environmental Health (CCCEH) at Columbia University's Mailman School of Public Health researchers found that cat ownership may have a protective effect against asthma symptoms in young children at age five.
Assistant professor of Environmental Health Sciences at the Mailman School of Public Health, lead author and investigator, Matthew Perzanowski, PhD, stated:
"While the study design does not allow us to recommend early cat ownership to prevent asthma, it does seem to indicate that avoidance of cats to prevent the development of asthma is not advised. However, once a child has asthma and is allergic to cats, the recommendation would still be to find a new home for the cat."
What Are the Statistics On Pet-Related Allergies?
As stated in a 2012 article by Lindsey Konkel in LiveScience titled Nothing to Sneeze At: Cats Worse Than Dogs for Allergies, about 10 percent of people are allergic to a household pet. But cat allergies were "twice as common as dog allergies" according to the American College of Allergy, Asthma and Immunology.
A 2011 article by Joe Brownstein in LiveScience revealed that when both boys and girls had a cat in their home during their first year of life, they reduced their risk of being sensitized to cats later in life by about 50 percent. Boys with a dog at home during their first year of life also showed about a 50 percent reduced risk of being sensitized (allergic) to dogs later on.
But (and this surprised me), girls with a dog at home during their first year had an increased risk of later being sensitized (allergic to dogs).
Confused? Me too. But keep in mind that the most recent Swedish study was conducted on over a million children. So, I am more swayed by the recent findings. Plus there seems to be other variables about cat dander that come into play (like the size of the protein molecule and whether its from a male or female cat).
Bottom Line: I'll take my baby to a petting zoo any time and I'll keep the family pets around (unless anyone in the family develops an allergy to any of them). As Dr. Virant concluded that unless mom or dad (or others in the family household) are allergic, "the more animals the better."