Secular Trends and Rural-Urban Differences in Diagnostic Prevalence of Hay Fever: A Claims-Based Study in Germany

Purpose: We aimed to examine possible variations in diagnostic prevalence of hay fever between urban and rural regions as well as in age-specific temporal developments.Patients and Methods: We used nationwide outpatient claims data from the years 2010 to 2019. The data contain information for all individuals with statutory health insurance (SHI) in Germany who were treated at least once in respective years (n = 71,410,121 in 2019). Individuals with a confirmed diagnosis of hay fever were defined as prevalent cases. We examined the association between the degree of urbanization and age-and sex-standardized prevalence of hay fever. We used the age-and sex-structure of SHI insurees in the year 2010 as a reference population for direct standardization.Results: The standardized prevalence of hay fever increased from 6.2% in 2010 to 7.2% in 2019, corresponding to a relative increase of 16%. However, we observed a clear decrease in prevalence among children, with the strongest relative reduction in young children (0-2 years: -53%). The standardized prevalence in the total population in 2019 was lowest in rural areas with a low population density (6.6%) and highest in big urban municipalities (7.8%). In stark contrast, prevalence in 0-14-year-olds was lowest in big urban municipalities (4.3%).Conclusion: We observed a decrease in the prevalence of hay fever in children and increase in the older age groups. A clear urban- rural association observed over years may be explained by environmental factors. Deviations from this general regional pattern in children of the age group 0-14 years may be explained by differing age-specific risk factors of hay fever.