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Data from Google Trends suggest ankle swelling is highly seasonal

Using population symptom data collected from Google Trends, researchers found high seasonality of internet searches for information on ankle swelling, according to findings published in the Annals of Family Medicine.

“Internet search volume has been used successfully to show unexpected seasonality in such conditions as nocturnal leg cramps,” Fangwei Liu, MD, from the department of family medicine at the University of Alberta and colleagues wrote. “Using similar methods, we looked for seasonal modulation in the public’s interest in ankle swelling as measured by the volume of Google internet searches related to ankle swelling.”

Due to increased volume of patients complaining of ankle swelling each summer, the researchers sought evidence that swelling is seasonally modulated in some patients.

Liu and colleagues used the Google Trends search engine, which provides information from 2004 onward about frequency of specified search terms entered by the public, to search any of “ankle swelling,” “swollen ankles,” or “swollen legs,” originating from the United States between Jan. 4, 2004, and Jan. 26, 2016. The researchers plotted internet search volume as a time series and performed regressions with two models that represented the null hypothesis (no seasonal variation) or the seasonal hypothesis (annual cycling in symptoms).

They found that the seasonal model provided a notably better fit compared with the null model (P < .0001), while seasonality explained 86% of the variability in search volume (R² = 0.86). The highest number of searches occurred in mid-June (midsummer) with the lowest in mid-December (midwinter). The researchers further confirmed by similar data in Australia when the reversed seasons followed the same pattern (R² = 0.73; 24.8-week phase difference).

“Disease seasonality, as we and others have shown, appears to be productively pursued using [Google Trends],” Liu and colleagues wrote. “Further research on patients with summertime ankle swelling would be needed to establish whether such patients have, or go on to develop, cardiovascular disease.”– by Savannah Demko