Objective: To determine the genetic component of time with middle ear effusion (MEE) and episodes of MEE and acute otitis media.
Design: Prospective twin/triplet cohort.
Setting: Research center at a tertiary pediatric hospital.
Participants: A total of 168 healthy same-sex twin and 7 same-sex triplet sets were recruited by age 2 months.
Interventions: Longitudinal assessment of middle ear status by pneumatic otoscopy and tympanometry at monthly evaluations, and at examinations during upper respiratory tract infections or symptoms of middle ear disease.
Outcome measures: Proportion of time with MEE and episodes of acute otitis media and MEE.
Results: Of the 140 sets for which zygosity was obtained, 114 were followed up to age 3 years and 83 sets to age 5 years. The heritability estimate for proportion of time with MEE in the first 5 years of life was 0.72 (P<.001). The correlation of proportion of time with MEE between children within a set was significantly higher in monozygotic sets (0.65-0.77) than in dizygotic sets (0.31-0.39) for each year to age 3 years. In the fourth and fifth years of life, the correlations decreased in both monozygotic and dizygotic twin sets.
Conclusions: Findings for the first 2 years of follow-up have been previously published and indicate a strong genetic component to the proportion of time with MEE. In the present report, which details the entire 5-year follow-up, the effect of this component appears to attenuate after the third year but its cumulative effect remains significant after 5 years.