[Comment] Uncovering the biases: why the claimed mask–excess mortality link fails to hold

The relationship between mask usage and excess mortality during the COVID-19 pandemic remains a subject of ongoing debate. A recent article by Tausk and Spira, “Does mask usage correlate with excess mortality? Findings from 24 European countries,”1 reported a positive correlation between mask use and excess mortality in 2020 and 2021. This finding attracted considerable attention, particularly in Brazil, where the authors are based. The study's ecological design, which is susceptible to bias when assessing individual-level exposures (such as mask use) compared to aggregate exposures (such as citywide pollution), has prompted widespread discussion on social media platforms.