Background: The risk factors for febrile, respiratory, and gastrointestinal illnesses in preschool children at day care centres have not been adequately identified and may differ between countries. Methods: In this repeated cross-sectional and longitudinal study of children at day care centres, we analyzed various potential risk factors for infectious illnesses using a mixed effect hierarchical Poisson regression model. The results of the analyses and the incidence rates of these illnesses are reported herein. Results: The study lasted 2.5 y (20002003) and was divided into five 6-month periods (seasons). Nine hundred and seventeen children participated, and their mean age within each season was 3.64.1 y. The only consistent risk factors identified were young age and winter season. No consistent risk factors at the day care centres (facilities or hygiene practices) were identified. The incidences of the febrile, respiratory, and gastrointestinal illnesses varied significantly between seasons (winter/summer) and between age groups. Conclusions: Risk factors of infectious illnesses are difficult to identify and because they may vary between countries, international recommendations on expensive intervention strategies are not justifiable. Rates of respiratory illnesses in Icelandic preschool children appear higher than in other countries, but rates of gastrointestinal illnesses lower.
This study was supported by grant QLK2-CT-2000-01020 (EURIS) from the European Commission and was a part of an international collaborative study, the European Resistance and Intervention Study (EURIS). It was also supported by a grant from The Icelandic Centre for Research (RANNIS). We would like to thank the staff and the parents at the participating day care centres for their invaluable help in carrying out the study.