Leveraging internet search data to assess prevalence, interest, and unmet needs of sarcoidosis in Germany.

Sarcoidosis is a multisystemic disease of connective tissue with granuloma formation of unknown etiology and unclear prevalence. Internet search data has been shown to correlate with disease incidences and the population's interest as well as seasonal variations. Accordingly, aim of this study was to leverage internet search data on sarcoidosis-related keywords to identify unmet needs, geographical and seasonal factors influencing sarcoidosis and estimating its prevalence. In this retrospective longitudinal study, Google Ads Keyword Planner was used to determine the internet search volume of terms related to sarcoidosis across Germany as a whole and in 17 major German cities between July 2015 and June 2019. Identified keywords were qualitatively categorized, converted into number of searches per 100,000 inhabitants and analyzed including regional and seasonal differences. With 3,068,200 queries and 425 different sarcoidosis-related search terms in the studied time period, the search volume was very high for a rare disease. Most searches (67.9%) related to general disease information with "sarcoidosis", "Löfgren's syndrome", "sarcoidosis lung", "Morbus Boeck" and "neurosarcoidosis" as the top five keywords. Searches per 100,000 inhabitants were comparable in all 17 cities but higher than in Germany as a whole. Overall, the search volume increased from 2015 to 2019 and peaked annually in European springtime with annual lows in European autumn and winter months. The overall high search volume suggests an unmet need for sarcoidosis-related information and a diagnostic gap. Seasonal fluctuations indicate environmental as well as climatic factors that may influence sarcoidosis.