Physical inactivity is associated with a higher risk for severe COVID-19 outcomes: a study in 48 440 adult patients
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    Put your trainer on hold; the causal relationship between physical inactivity and severe COVID-19 is still not clear.
    • Edel T O'Hagan, Doctoral candidate Centre for Pain IMPACT, Neuroscience Research Australia, Sydney and Prince of Wales Clinical School, UNSW
    • Other Contributors:
      • Rodrigo RN Rizzo, Doctoral candidate
      • Michael A Wewege, Doctoral candidate
      • James H McAuley, Professor
      • Matthew D Jones, Lecturer

    Dear Editor,

    Sallis and colleagues showed that patients who were not consistently meeting physical activity guidelines prior to COVID-19 contamination had a substantially greater risk of hospitalisation, admission in intensive care units, and death than patients who were consistently meeting physical activity guidelines (>150min/week engaging in moderate or strenuous exercise over 2-months).1 Identifying risk factors associated with negative COVID-19 outcomes is timely. COVID-19 has resulted in almost 3,000,000 deaths worldwide by the middle of April 2021 2, and vaccination seems insufficient without health and political behaviour changes. 3

    However, we have some concerns about Sallis and colleague’s conclusions. The authors recommended “efforts to promote physical activity” relied on strong assumptions that meeting physical activity guidelines would cause less COVID-19 negative outcomes such as hospitalisation, admission in intensive care units, and deaths. Although exercise has many benefits to individuals, we cannot allow that the urgency of solving problems lead to hasty and imprecise conclusions of causality, as well as unnecessary efforts for implementation.

    Consider a “0-10 causality strength scale”, proposed by Pearl (2018) 4, where 0 is weak evidence of causality and 10 is strong evidence of causality. Depending on the assumptions and procedures used in the studies to test the association between variables, we become more or less confident...

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    Conflict of Interest:
    None declared.