[Nasal congestion and earache--upper respiratory tract infections in 4-year-old children].
BACKGROUND: Few population-based studies in Norway have addressed upper respiratory infections in children. MATERIAL AND METHODS: A questionnaire concerning health, diseases and living condition was administered to parents of all four-year-old children in Vestfold county (n = 1912). Participation rate was 79%. RESULTS: Close to one out of three of the children suffered from recurrent common cold (four episodes or more) during the last year. One third experienced otitis at least once, and one out of twenty experienced four episodes of otitis or more. Day-care centre attendance was the only significant risk factor for recurrent common cold (odds ratio 1.50; 95% CI 1.18-1.92) or otitis (odds ratio 1.42; 95% CI 1.12-1.77). The odds ratios were essentially unchanged after logistic regression analysis, when mother's education, housing, other children in the family, passive smoking, and history of breastfeeding were included in the analysis. Children with otitis or recurrent common cold consulted a doctor almost ten times as often as other children. INTERPRETATION: Day-care centre attendance has significant influence on the occurrence of upper respiratory infections in four-year-olds, but less influence than reported for younger children. Other environmental differences seem to be of little importance and do not represent any potential for prophylaxis.