A few days ago, I wrote a blog post about pet dogs reducing asthma risk in children. Well, it looks like yet another study was published online today in the journal Pediatrics is making headlines. The article, "Respiratory Tract Illnesses During the First Year of Life: Effect of Dog and Cat Contacts," investigated "the effect of dog and cat contacts on the frequency of respiratory symptoms and infections during the first year of life." The research, conducted in Finland, studied 397 children who "were followed up from pregnancy onward, and the frequency of respiratory symptoms and infections together with information about dog and cat contacts during the first year of life were reported by using weekly diaries and a questionnaire at the age of 1 year."
The researchers through the weekly diaries and questionnaires "evaluated respiratory infectious symptoms (cough, wheezing of breath, rhinitis, and fever) and infections (middle ear infection)" in study children. Families were also asked through the "weekly questionnaires whether they had a dog or a cat at home and how much time it had spent inside daily. For the following analysis, dog and cat contacts indoor at home were grouped into: (1) no contact at all; (2) low contact (pet inside at home up to a maximum of 6 hours daily); (3) medium contact (pet inside from 6–16 hours daily); and (4) high contact (pet inside > 16 hours daily). Breastfeeding was reported in 3 categories weekly: the child had either been solely breastfed, partly breastfed, or not breastfed at all." Children were also grouped "depending on the birth month: summer (June–August), autumn (September–November), winter (December–February), and spring (March–May)."
"The most frequently reported disease was rhinitis, which occurred in 17.0% of the follow-up weeks. Cough occurred in 10.4%, fever in 4.0%, wheezing in 2.0%, and middle ear infection in 2.5% of the follow-up weeks." "According to the 1-year retrospective questionnaire at the end of the study period, 65.2% of the children lived mainly in homes with no dog contact and 75.5% in homes with no cat contact. During the pregnancy, 22.7% of families reported pet animal avoidance due to allergic symptoms in the family. If children had dog or cat contacts at home, they were significantly healthier during the study period in univariate tests (both P < .001) and had fewer weeks with cough, otitis, and rhinitis and also needed fewer courses of antibiotics than children with no cat or dog contacts at all."
"Even after adjusting for possible confounders, children having a dog at home were significantly healthier, had less frequent otitis, and tended to need fewer courses of antibiotics during the study period than children without dog contacts. Both the weekly amount of dog contacts (according to diary data) and the average amount of yearly contact (according to 1-year questionnaire data) with dogs was associated similarly with decreasing respiratory infectious disease morbidity. The highest protective association between dog ownership and healthiness, as well as lower risk for antibiotic use, otitis and rhinitis was detected among children who had a dog inside at home for < 6 hours daily (according to diary data) or had a dog temporally or often inside (according to retrospective data) compared with those who did not have any dogs or dogs were not inside."
"According to our results, dog and cat contacts during early infancy may be associated with less morbidity in general (indicated as more healthy weeks) and concomitantly may have a protective effect on respiratory tract symptoms and infections. In comparisons between cat and dog contacts, dog contacts showed a more significant protective role on respiratory infectious disease morbidity." The researchers "showed that children who had dog contacts at home had less otitis and rhinitis and more healthy weeks than children without dog contacts at home, but having a dog at home during the first postnatal year had no significant role in the occurrence of wheezing and cough, which is in line with earlier results, even though the reason for these findings is obscure. Cat ownership seemed to also have an overall protective effect, although weaker than dog ownership, on the infectious health of infants." "It is unsure why cat exposure is less significant compared with dog exposure."
An interesting finding of the study is, "children living in houses in which dogs spend only part of the day inside (defined as < 6 hours or temporally) had the lowest risk of infectious symptoms and respiratory tract infections. A possible explanation for this interesting finding might be that the amount of dirt brought inside the home by dogs could be higher in these families because they spent more time outdoors. In other words, less dirt is brought indoors by dogs who mainly live indoors. The living environment could also affect the amount of dirt and animal contacts." The researchers theorize that "The amount of dirt is likely to correlate with bacterial diversity in the living environment, possibly affecting the maturation of the child’s immune system and further affecting the risk of respiratory tract infections."
"Evidence suggests that animal contacts, especially during early life, might be crucial in immunity developing along a nonallergic route and in ensuring effective responses to respiratory viral infections in early life. We speculate that animal contacts could help to mature the immunologic system, leading to more composed immunologic response and shorter duration of infections. We offer preliminary evidence that dog ownership may be protective against respiratory tract infections during the first year of life."
This study once again reinforces the notion of the "hygiene hypothesis." "The dirt and germs a dog brings into the house may cause a child's immune system to mature faster, which makes it better at defending against the viruses and bacteria that cause respiratory problems."
There are several things that I can take away from this study. I need to love my dog even more for the "protection" she is imparting to my children's immune systems and I probably need to let her run around in the dirt more outside. In the often hectic schedule of my life, I find myself not letting the dog spend as much time outdoors. It is easier to keep her inside where I can keep an "eye" on her. If I let her spend more time outdoors, she will bring in more dirt and as a result make my children's immune systems stronger... At least that is what I can tell my husband the next time he comes home to dirty floors.