- Children who had a dog at home had fewer respiratory tract symptoms than children with no dog contacts.
- Note that children having dog contacts at home had less frequent otitis and tended to need fewer courses of antibiotics than children without such contacts.
Having a dog in the home can help ward off infections in very young infants, possibly by hastening immune system development, researchers suggested.
During the first year of life, children living with dogs were generally healthier (OR 1.31, 95% CI 1.13 to 1.52, P<0.001) and were less likely to have frequent ear infections (OR 0.56, 95% CI 0.38 to 0.81, P=0.002), according to Eija Bergroth, MD, of Kuopio University Hospital in Kuopio, Finland, and colleagues.
In addition, they typically were treated with fewer courses of antibiotics for otitis (OR 0.71, 95% CI 0.52 to 0.96, P=0.03) compared to children without contact, the researchers reported in the August Pediatrics online.
Previous studies concerning the presence of animals in the home and childhood immunity have had conflicting results, with some suggesting that living with dogs can have favorable effects, while others found an increased risk for respiratory infections in children with pets.
"A better understanding of the interplay between pet-related exposures and the development of early respiratory tract infections may provide indirect insight regarding the factors affecting the maturation of the immune responses and its disturbances," Bergroth and colleagues wrote.
To explore this, the researchers enrolled 397 Finnish newborns, requesting that their parents fill out weekly diaries on symptoms, infections, and pet exposures beginning at week 9 of life and continuing through the first year.
The parents also completed a retrospective questionnaire at the conclusion of the study.
During a total of 17,124 weeks of follow-up, fever had been reported in 71.8% of the children, otitis media in 39.5%, rhinitis in 96.7%, cough in 84.4%, and wheezing in 32.2%.
Systemic antibiotics had been given to 47.6%.
On the retrospective questionnaire, having no dog exposure at home was reported for 65.2% of the children, while 75.5% had no cat exposure.
In a univariate analysis, having either a dog or a cat was associated with better overall health (P<0.001), with children having fewer weeks during which they had respiratory tract symptoms.
However, in the multivariate analysis with adjustment for confounders including sex, rural living, maternal smoking, number of siblings, parental allergies, and season of birth, only having a dog at home was significant.
When the researchers considered the extent of canine exposure (less than 6 hours per day, 6 to 16 hours, or more than 16 hours), they found the strongest associations for having a dog inside the house for less than 6 hours per day:
- Overall healthy, OR 1.25 (95% CI 1.04 to 1.50, P=0.02)
- Fever, OR 0.63 (95% CI 0.41 to 0.97, P=0.04)
- Antibiotic use, OR 0.54 (95% CI 0.34 to 0.87, P=0.01)
- Otitis, OR 0.38 (95% CI 0.18 to 0.82, P=0.01)
As to why having the dog inside for a shorter period of time would be more protective, the researchers suggested that dogs that were outdoors longer could have tracked more dirt into the house.
"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," Bergroth and colleagues observed.
Although cat ownership seemed protective in the univariate analysis, the association for overall health was not significant in the multivariate analysis (OR 1.06, 95% CI 0.88 to 1.29, P=0.53).
The reasons for this were unclear, the researchers noted.
The study provides "preliminary evidence" that having a dog in the home may have beneficial effects on early immunity, and particularly for preventing respiratory tract infections, they concluded.
Primary source: Pediatrics
Bergroth E, et al. "Respiratory tract illnesses during the first year of life: Effect of dog and cat contacts" Pediatrics 2012; DOI: 10.1542/peds.2011-2825.