Introduction
Ample evidence exists that there has been a dramatic increase in the prevalence of childhood asthma through the 1980s and 1990s in westernised countries. Many spoke of an ‘asthma epidemic’ and there has been broad discussion on the underlying causes and the burden of the disease on patients and society1-7. However, studies conducted in the first two decades of the 21st century suggested that asthma prevalence may have reached a plateau or even be declining8-15. In the initial phase of the International Study of Asthma and Allergies in Childhood (ISAAC I), particularly high asthma rates were reported in English speaking countries16. But in ISAAC III, 5-10 years later, these countries showed a significant decline, despite the slight worldwide increase in the prevalence of childhood asthma17. This was also the case in a study based on 2001-2013 data from the USA18 and in the Aberdeen surveys that cover a period of 50 years (1964-2014)14,15. In contrast to the ‘asthma epidemic’, however, the reversing trend in the prevalence of childhood asthma is difficult to explain12,15,18.
The Patras respiratory school surveys6,7,19, a series of repeated questionnaire-based studies of 8-9-year-old schoolchildren in the city of Patras, Greece, demonstrated a continuous rise in the prevalence of wheeze/asthma from 1978 to 20036,7, followed by a plateau phase between 2003 and 200819. Two identical follow-up surveys were conducted in 2013 and 2018, while in the latter study spirometry was also performed in children with a positive history of wheeze/asthma and in a random sample of negative controls. Here, we present the results of the last two surveys, aiming to provide data on the prevalence trends of childhood asthma over a period of 40 years (1978-2018) in an urban environment in Greece.