The role of climate on the geographic variability of asthma, allergic rhinitis and respiratory symptoms: results from the Italian study of asthma in young adults


Prof. Roberto de Marco
Sezione di Epidemiologia & Statistica Medica
Dipartimento di Medicina e Sanità Pubblica
Università degli Studi di Verona
c/o Istituti Biologici II
Strada Le Grazie 8
37134 Verona


Background:  Variations in the prevalence of respiratory symptoms according to geo-climatic factors could provide important clues to the knowledge of the aetiology of asthma.

Methods:  Geo-climatic variations in the prevalence of current asthma, allergic rhinitis and chronic cough, and phlegm were assessed on a random sample of 18 873 subjects (response rate = 72.7%) from different climatic regions of Italy. An ecological analysis, supported by robust statistical methods, was employed to investigate potential trends.

Results:  The prevalence of all symptoms was significantly heterogeneous throughout the peninsula. Only asthma-like symptoms showed a north–south trend: the prevalence increased at a decreasing latitude [odds ratio (OR) varies from 0.92 to 0.96, P < 0.05], at a decreasing distance from the sea (OR: 0.90–0.93 for 30 km distance, P < 0.05), at higher annual mean temperatures (OR: 1.11–1.14, P < 0.05) and at smaller annual temperature ranges (OR: 0.94–0.95, P < 0.05). Of the geo-climatic variables considered, temperature range had the greatest influence on most asthma-like symptoms. No association was found between geo-climatic variables and allergic rhinitis or chronic cough and phlegm.

Conclusions:  Asthma prevalence seems to be significantly affected by climate as asthma-like symptoms were more common in central-southern Italy, with a Mediterranean climate, than in areas with a continental climate (northern Italy).