Otitis media with effusion and habitual mouth breathing in Dutch preschool children.

Habitual mouth breathing (HMB) is defined as the habit of in- and exhaling (part of) the air through the mouth, when an individual is at rest and the nose is sufficiently free. It is postulated that HMB is a risk factor for otitis media with effusion (OME) in preschool children. The results are presented of a prospective cohort study on 253 3-year-old children, free from OME, with a follow-up period of 3 months, to determine the role of HMB in the etiology of OME. The risk ratio for OME of habitual mouth breathers, compared to nose breathers, was found to be 2.4 (95% confidence interval (C.I.): 0.99-5.70). Moreover, there is a clear and significant linear trend in the proportion of OME in 3 breathing categories: nose breathing, intermediate and mouth breathing. This relation remains after correction for confounding. It is concluded that HMB is a risk factor for OME. It is estimated that about 20% of the incidence of OME is caused by HMB. The high incidence of OME means that HMB carries a great deal of impact. Suggestions are made for the prevention and treatment of HMB.