Seasonal variation in the prevalence of persistent otitis media with effusion in one-year-old infants.

The objective of this population-based cohort study was to evaluate the prevalence of persistent otitis media with effusion (OME) and its seasonal variation in 12-month-old infants. All 30099 infants born in the eastern part of The Netherlands between 1 January 1996 and 1 April 1997 were invited for hearing screening, comprising a protocol of three possible tests. Those who failed all three screening tests were referred to an ENT clinic for examination. Prevalences (i.e. the probability that a child would fail all the screening tests) were calculated by searching for the best logistic model for the first, second and third screening test as well as for the visit to an ENT department. By multiplying the prevalences found by the different models with each other, a prevalence was calculated that accounted for increasing age and the timing of the successive hearing tests. Furthermore, 95% confidence intervals were calculated for this age-season-corrected prevalence. When all the children attended the hearing tests at 9, 10, 11 and 12 months of age and when the number of births was the same in all months, the overall prevalence was 4.8% [95% CI 4.3, 5.2]. The highest prevalence (8.0%) was found in April, and the lowest (1.5%) in October. Rates of bilateral OME during the late winter months were twice as high as those during the late summer.