A prospective epidemiological investigation of secretory otitis media and tubal dysfunction in children attending day-care centers. Serial tympanometry with an interval of two weeks.

The present investigation included 373 children aged 9 months to 7 years, cared for in nine kindergartens and one nursery home. Serial tympanometries were carried out at 2-week intervals. A Madsen Electronics ZS 330 tympanoscope was used for the measurements. To identify A, C1, C2 and B tympanograms, middle ear pressure, compliance and stapedial reflex were measured. After correction for age and other factors which could influence the prevalence of B and C2 tympanograms (number of siblings and parental smoking, which was included in an investigation of the indoor environment of the same children), no significant difference was found in the prevalence of these types of tympanograms, even though the number of children attending the different day-care centers ranged from 19 to 72. No significant difference was found in the prevalence of the A, C1, C2 and B tympanograms between right and left ears, but there was a significant difference in the prevalence of the A tympanograms in boys and girls, but not in C1, C2 and B tympanograms. The maximum prevalence of B tympanograms was found in 1-year-old children, decreasing to the age of 7 years.