Comment: The level of evidence is downgraded by inconsistency (unexplained variability in results).
In a cohort study by Sipilä et al 1 comprising 1 642 children, the children were followed up from the age of about 6 months to the age of 18 months. By the age of one year, 45.3% of the children had had at least one episode of otitis media. By the age of 18 months 56.7% had had as least one and 29.8% at least three episodes of acute otitis media.
Similar figures were obtained in a study by Alho et al 2 in which 2 512 children were followed up from birth until the age of two years. By the age of one year, 42.4% (95% Cl 40.4 to 44.4%) of the children had had at least one episode of acute otitis media. By the age of two years the corresponding percentage was 71.0% (95% confidence interval 68.9 - 73.1%).
Even higher figures were reported in a study by Teele et al 3 in which 498 children were followed up to the age of seven years. During the first year of life the cumulative incidence of otitis media in these children was 62%, by the age of three years 84% and by the age of five 91%. It is, however, possible that the rather high percentages observed in this study are at least partly explained by the fact that a considerable number of children were lost from the study during the follow-up (originally the study enrolled 1 067 children).
In a study from Taiwan 4, comparative analysis showed that the overall prevalence of AOM among children younger than 5 years was only 20%. AOM was more prevalent during the spring season, and still was similarly common after age 2 years.
In a study from New Zealand 5, the raw incidence of AOM in children under 5 years of age was 273 per 1000 children (27.3%; 95% CI 216-330).
In a Japanese study 6, approximately 4-5% of pediatric outpatients, even without AOM-related symptoms, had AOM.
In an epidemiological, observational cohort study 7 data on physician-diagnosed AOM from 5776 children were collected from retrospective review of medical charts for the year preceding enrolment and prospectively in the year following enrolment. The study included children in Germany, Italy, Spain, Sweden, and the UK. The enrolment was balanced between the 0-2 and 3-5 years age groups. AOM incidence was 256/1000 person-years [95% CI 243-270] in the prospective study period. Incidence was lowest in Italy (195, 95% CI 171-222) and highest in Spain (328, 95% CI 296-363). The incidence rate was higher in the 0-2 years age group (299, 95% CI 279-320) than in the 3-5 years age group (212, 95% CI 195-230). Complications were documented in <1% of episodes. Spontaneous tympanic membrane perforation was documented in 7% of episodes. Both retrospective and prospective study results were similar and show the high incidence during childhood in these 5 European countries. Differences by country may reflect true differences and differences in social structure and diagnostic procedures.
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