Regional variations and prevalence of psoriasis in Germany from 2010 to 2017: a cross-sectional, spatio-epidemiological study on ambulatory claims data

Objectives Global prevalence rates of psoriasis differ significantly, with lowest rates in the equator region and increasing tendencies towards the north but also differences within-country. Information on regional variations in Germany is missing. This study aims to analyse the change of psoriasis prevalence in Germany over time and to detect regional variations. Design Cross sectional, spatio-epidemiological study on regional psoriasis prevalence in Germany. Setting Claims data study based on nationwide outpatient billing data on county level. Methods Analyses based on outpatient billing data for 2010-2017 derived from all people insured in statutory health insurances (about 72.8 million). We performed descriptive spatio-temporal analyses of prevalence rates using probability mapping and statistical smoothing methods, identified spatial clusters and examined a north-south gradient using spatial statistics. Results The prevalence increased from 147.4 per 10 000 in 2010 to 173.5 in 2017. In 2017, counties' prevalence rates ranged between 93.8 and 340.9. Decreased rates occurred mainly in southern counties, increased rates in northern and eastern counties. Clusters of low rates occur in southern and south-western Germany, clusters of high rates in the north and north-east. The correlation between counties' latitudes and their prevalence rates was high with Pearson's r=0.65 (p<0.05). Conclusion Increased prevalence of psoriasis over time and marked regional variations in Germany were observed which need further investigation.