Dynamic multivariate modelling: day care and consultation rate for acute otitis media

A random sample of 2,512 children was monitored to the age of 2 years to study the effects of various risk variables on the consultation rate of acute otitis media. A total of 3,283 episodes of acute otitis media of 2,411 children with a follow-up time of at least 1 month were included in the analysis. During a 3 week-period after onset of the episode, the number of unplanned visits varied between 0 (2,544 episodes; 77.5%) and 6 (2 episodes; 0.1%). The children with day care outside their home showed a diminished risk for unplanned visits during the first week. The odds ratio (OR) and 95% confidence interval (CI) for children in family day care were 0.58 and 0.39-0.8, and 0.72 and 0.47-1.11 for children in nursery day care, respectively. During the second and third weeks the results were reversed: the above odds ratios should be multiplied by interaction terms 2.19 (CI 1.41-3.42; new OR 1.27) for children in family day care and 1.57 (CI 0.97-2.54; new OR 1.13) for children in nursery day care.