Seasonal variation of diseases in children: a 6-year prospective cohort study in a general hospital

Seasonal variation in pediatrics has been well described in some infectious diseases, asthma, and diabetes, but data on seasonality for other diseases in children are sparse. To explore the extent of seasonal variation of the entire pediatric field, we analyzed diagnostic codes of all newly referred patients (n = 51,054) to our pediatric department of a large teaching hospital in the Netherlands over a 6-year period (2008-2013). Seasonality was analyzed using simple moving averages, the standard error of the mean (SEM) and the percentage monthly variation. We defined seasonal variation as a visually recognizable periodic pattern in every year in combination with a standard error of the mean > 0.20. Four diseases fulfilled our definition of seasonality: respiratory tract infections (peak in January, +107.0 %), gastroenteritis (peak in February-March, +95.8 % and +112.9 %, respectively), functional complaints (peak in March, +34.0 %, and November, +13.4 %), and asthma (peak in March, +27.8 %, and October, +17.5 %). Together, these four categories comprised 21.2 % of all newly referred patients. Conclusion: Seasonal variation occurs in more than one fifth of all patients with pediatric disease. We demonstrated not only seasonal variation for respiratory tract infections, gastroenteritis, and asthma, but also for functional complaints