Seasonal variation for plantar fasciitis: evidence from Google trends search query data

Key points

1. 01Used Google Trends monthly search volume for the terms plantar fasciitis and heel pain from January 2009 to December 2019.
2. 02Six native English-speaking countries were studied across both hemispheres: USA, Canada, the U.K., Ireland, Australia, and New Zealand.
3. 03Searches peaked in summer and reached a trough in winter, and the northern and southern hemispheres were out of phase by about 6 months, suggesting a true seasonal rather than calendar effect.
4. 04For plantar fasciitis the seasonal pattern was statistically significant in all six countries; for heel pain it was significant in five, with New Zealand falling short.
5. 05The leading explanation is that warmer months bring more walking and running, which raises the risk of plantar fasciitis.

How it was conducted

Design

Retrospective analysis of internet search query data (Google Trends), no patients enrolled

Data source

Monthly relative search volume from Google Trends, January 2009 to December 2019

Search terms

plantar fasciitis and heel pain

Regions

USA, Canada, the U.K., Ireland, Australia, and New Zealand

Statistical analysis

Cosinor (sinusoidal) model to estimate seasonal amplitude, peak month, and significance; significance set at p < 0.025

What they found

• For the term plantar fasciitis, seasonality was significant in all six countries: USA (A = 10.45, p < 0.001), Canada (A = 13.14, p < 0.001), the U.K. (A = 7.03, p < 0.001), Ireland (A = 7.32, p = 0.007), Australia (A = 6.86, p = 0.004), and New Zealand (A = 9.34, p < 0.001).
• For the term heel pain, seasonality was significant in five countries: USA (A = 12.45, p < 0.001), Canada (A = 11.75, p < 0.001), the U.K. (A = 7.86, p < 0.001), Ireland (A = 6.91, p = 0.01), and Australia (A = 5.47, p = 0.002).
• For heel pain in New Zealand, the trend was similar but did not reach significance (A = 6.69, p = 0.07).
• Search peaks fell in summer (July in northern hemisphere countries, February or January in the southern hemisphere) and troughs in winter, with the hemispheres out of phase by about 6 months.
• Relative search volume for both terms steadily increased from January 2009 to December 2019 across all six countries.

Limitations

• Google Trends gives no demographics (age, education, income), so searchers do not necessarily reflect the actual patient population and results cannot be generalized.
• Only six countries were analyzed, so differences in climate, race, and social conditions could not be assessed.
• People may search for a condition without having it (for example media coverage, health campaigns, or research), and the study did not account for these influences.
• Only the Google search engine was used, introducing possible selection bias, and the study could not explain the clinical mechanism behind the seasonal pattern.

Why it matters

For patients

If your heel pain tends to flare in summer, it may track with the season's higher activity levels, so easing into long walks or running can help.

For clinicians

Expect plantar fasciitis presentations to rise in the warmer months, which can inform staffing, patient counseling, and prevention messaging.

For readers

This shows how freely available internet search data can reveal real seasonal disease patterns that mirror findings from clinical databases.