Cancer Internet search activity on a major search engine, United States 2001-2003

Background: To locate online health information, Internet users typically use a search engine, such as Yahoo! or Google. We studied Yahoo! search activity related to the 23 most common cancers in the United States. Objective: The objective was to test three potential correlates of Yahoo! cancer search activity-estimated cancer incidence, estimated cancer mortality, and the volume of cancer news coverage-and to study the periodicity of and peaks in Yahoo! cancer search activity. Methods: Yahoo! cancer search activity was obtained from a proprietary database called the Yahoo! Buzz Index. The American Cancer Society's estimates of cancer incidence and mortality were used. News reports associated with specific cancer types were identified using the LexisNexis "US News" database, which includes more than 400 national and regional newspapers and a variety of newswire services. Results: The Yahoo! search activity associated with specific cancers correlated with their estimated incidence (Spearman rank correlation, p = 0.50, P =.0 15), estimated mortality (p = 0.66, P =.001), and volume of related news coverage (p = 0.88, P <.001). Yahoo! cancer search activity tended to be higher on weekdays and during national cancer awareness months but lower during summer months; cancer news coverage also tended to follow these trends. Sharp increases in Yahoo! search activity scores from one day to the next appeared to be associated with increases in relevant news coverage. Conclusions: Media coverage appears to play a powerful role in prompting online searches for cancer information. Internet search activity offers an innovative tool for passive surveillance of health information-seeking behavior.