Genetics and Ear-Infection

Genetics appears to play a major role in how susceptible a child is to getting infections in the middle ear, a new study finds.

Otitis media, or middle ear infection, is the No. 1 reason children are prescribed antibiotics or have surgery. Untreated, the infections, which most often afflict infants and children under age 10, can lead to hearing loss and learning delays. While environmental causes such as exposure to smokers or other infected children are known to contribute to otitis media, it has been suspected that the predisposition to the infection is inherited.

Researchers at the University of Pittsburgh School of Medicine designed a study that separated environmental factors from genetic ones. In the study, published in the Journal of the American Medical Association, 135 pairs of same-sex twins and five sets of same-sex triplets were followed from the age of 2 months to 2 years old. Fifty-four percent were identical twins, meaning they have the same genes, and 46 percent were nonidentical.

The researchers found that identical siblings were more likely to spend the same amount of time with fluid in the middle ear - one of the symptoms and results of middle ear infections - compared with nonidentical twins or triplets: Heredity accounted for 73 per cent of the amount of time a child had middle ear effusion, or fluid, the researchers found. Moreover, nonidentical twins or triplets were far more likely to have acute bouts of otitis media at different times than their twin or triplet siblings, compared to identical twins or triplets. Being aware of a possible family susceptibility to otitis media may help parents and pediatricians, said the chief researcher, Dr. Margaretha Casselbrant. Breast feeding infants, not putting a young child in day care and not exposing them to secondhand smoke may help decrease a high-risk child's susceptibility to the infections, she said.