•Statistically significant improvements are seen for mortality, ventilation, ICU admission, hospitalization, recovery, and cases. 26 studies from 26 independent teams in 14 different countries show statistically significant
improvements in isolation (19 for the most serious outcome).
•Results are robust — in exclusion sensitivity analysis 28 of 33
studies must be excluded to avoid finding statistically significant efficacy
in pooled analysis.
•Results are consistent with the overall risk of all cause mortality based on cardiorespiratory fitness — [Laukkanen] show RR 0.55 [0.50-0.61] for the top vs. bottom tertiles.
•Studies analyze exercise/physical activity levels before infection, comparing regular/moderate exercise vs. lower/no exercise. Note that risk may increase with more extreme activity levels.
•No treatment, vaccine, or intervention is 100%
available and effective for all variants. All practical, effective, and safe
means should be used.
Denying the efficacy of treatments increases mortality, morbidity, collateral
damage, and endemic risk.
•All data to reproduce this paper and
sources are in the appendix.
[Rahmati] present another meta analysis for exercise, showing significant improvements for mortality, ICU admission, and hospitalization.
Figure 1.A. Random effects
meta-analysis. This plot shows pooled effects, discussion can be found in the heterogeneity section,
and results for specific outcomes can be found in the individual outcome analyses.
Effect extraction is pre-specified, using the most serious outcome reported.
For details of effect extraction see the appendix.
B. Scatter plot showing the
distribution of effects reported in studies. C. History of all reported
effects (chronological within treatment stages).
We analyze all significant studies
reporting COVID-19 outcomes as a function of physical activity levels.
Search methods, inclusion criteria, effect
extraction criteria (more serious outcomes have priority), all individual
study data, PRISMA answers, and statistical methods are detailed in
Appendix 1. We present random effects meta-analysis results for all
studies, for studies within each treatment stage, for individual outcomes, for
peer-reviewed studies, for Randomized Controlled Trials (RCTs), and after
exclusions.
Insufficient physical activity is a risk factor for many
diseases and is common around the world [Guthold], as shown in
Figure 2. [Guthold] found that prevalence in high-income
countries was over twice as high, and has increased over time.
Figure 2. Prevalence of insufficient
physical activity around the world as of 2016, from [Guthold] (top: female,
bottom: male).
For upper respiratory tract infections, research shows lower risk
for moderate activity vs. a sedentary lifestyle, however risk increases with more
extreme activity levels [Nieman].
Figure 3 shows a visual overview of the results, with details in
Table 1 and Table 2.
Figure 4, 5, 6, 7, 8, 9, 10, and 11
show forest plots for a random effects meta-analysis of
all studies with pooled effects, mortality results, ventilation, ICU admission, hospitalization, recovery, cases, and peer reviewed studies.
Figure 4. Random effects meta-analysis for all studies with pooled effects.
This plot shows pooled effects, discussion can be found in the heterogeneity section,
and results for specific outcomes can be found in the individual outcome analyses.
Effect extraction is pre-specified, using the most serious outcome reported.
For details of effect extraction see the appendix.
Figure 11. Random effects meta-analysis for peer reviewed studies.
[Zeraatkar] analyze 356 COVID-19 trials, finding no
significant evidence that peer-reviewed studies are more trustworthy.
They also show extremely slow review times during a pandemic. Authors
recommend using preprint evidence, with appropriate checks for potential
falsified data, which provides higher certainty much earlier.
Effect extraction is pre-specified, using the most serious outcome reported,
see the appendix for details.
To avoid bias in the selection of studies, we analyze all
non-retracted studies. Here we show the results after excluding studies with
major issues likely to alter results, non-standard studies, and studies where
very minimal detail is currently available. Our bias evaluation is based on
analysis of each study and identifying when there is a significant chance that
limitations will substantially change the outcome of the study. We believe
this can be more valuable than checklist-based approaches such as Cochrane
GRADE, which may underemphasize serious issues not captured in the checklists,
overemphasize issues unlikely to alter outcomes in specific cases (for
example, lack of blinding for an objective mortality outcome, or certain
specifics of randomization with a very large effect size), or be easily
influenced by potential bias. However, they can also be very high
quality.
The studies excluded are as below.
Figure 12 shows a forest plot for random
effects meta-analysis of all studies after exclusions.
[Brawner], unadjusted results with no group details.
[de Souza], unadjusted results with no group details. Excluded results: mechanical ventilation.
[Huang], unadjusted results with no group details. Excluded results: severe case.
[Kontopoulou], unadjusted results with no group details.
[Mohsin], unadjusted results with no group details.
[Yuan], excessive unadjusted differences between groups. Excluded results: death.
Figure 12. Random effects meta-analysis for all studies after exclusions.
This plot shows pooled effects, discussion can be found in the heterogeneity section,
and results for specific outcomes can be found in the individual outcome analyses.
Effect extraction is pre-specified, using the most serious outcome reported.
For details of effect extraction see the appendix.
More physically active people have reduced risk for COVID-19.
Statistically significant improvements are seen for mortality, ventilation, ICU admission, hospitalization, recovery, and cases. 26 studies from 26 independent teams in 14 different countries show statistically significant
improvements in isolation (19 for the most serious outcome).
Meta analysis using the most serious outcome reported shows
39% [31‑46%] improvement. Results are similar after exclusions and similar for peer-reviewed studies.
Results are robust — in exclusion sensitivity analysis 28 of 33
studies must be excluded to avoid finding statistically significant efficacy
in pooled analysis.
Results are consistent with the overall risk of all cause mortality based on cardiorespiratory fitness — [Laukkanen] show RR 0.55 [0.50-0.61] for the top vs. bottom tertiles.
Studies analyze exercise/physical activity levels before infection, comparing regular/moderate exercise vs. lower/no exercise. Note that risk may increase with more extreme activity levels.
