Background Literature on health promotion evaluation and public understanding of health suggests the importance of investigating behaviour over time in conjunction with information environment trends as a way of understanding programme impact. We analysed population response to online promotion of an educational tool built by the Ask About Aspirin campaign in the USA to inform people about aspirin as a preventive aid.

Methods We collected 156 weeks of time series data on audience behaviour, namely use of a self-assessment tool. We then used the Autoregressive Integrated Moving Average (ARIMA) modelling to predict that outcome as a function of paid search engine advertising, paid social media promotion and general search interest in aspirin.

Results Through ARIMA modelling of tool engagement data adjusted for outcome series autocorrelation, we found a significant effect of online promotional effort on audience behaviour. Total paid search advertising positively predicted weekly total of individuals who started using the self-assessment tool, coefficient=0.023, t=3.28, p=0.001. This effect did not appear to be an artefact of broader secular trends, as Google search data on the topic of aspirin use did not add explanatory power in the final model nor did controlling for general search interest eliminate the significant coefficient for paid search promotion.

Conclusion Results hold implications both for educational tool development and for understanding health promotion campaign effects. We witnessed substantial but ephemeral effects on tool use as a function of paid search efforts, suggesting prioritisation of efforts to affect search engine results as a dissemination tactic.