Prospective analysis: does ice bathing harden against COVID-19 and is B RhD- the least viral resistant blood group in Polish ice bathers?

Background. Amateur ice bathing has recently become very popular, with studies revealing health benefits, including enhanced viral resistance. Such interest in this issue has been heightened even more due to the COVID-19 pandemic. The study predates widespread COVID-19 vaccination in Poland. Objectives. The aim of the study was to investigate the effect of short-term cold-water immersion on COVID-19 resistance in Polish ice bathers. Additionally, a possible relation between the ABO blood group and RhD antigen of winter swimmers and COVID-19 incidence was also studied. Material and methods. A survey was conducted on 2,534 Polish ice bathers who were questioned about their demographic data, ice bathing habits, ABO and RhD antigens, symptoms of infection and SARS-CoV-2 RT-PCR test results. For prospective statistical analysis, a Bayesian prediction was carried out to accommodate for missing COVID-19 RT-PCR test data following the selected explanatory clinical covariates. Furthermore, a taxonomic method was used to cluster the ice bathers. Results. In experienced ice bathers, a 7% higher resistance to COVID-19 has been estimated compared to beginners. Additionally, the probability of COVID-19 infection in ice bathers with blood group B RhD- is predicted to be the highest, while group O RhD+ and A RhD+ tend to be more resistant against the virus. Conclusions. There is an increasing immunological resistance of ice bathing, especially in O RhD+ and A RhD+ carriers, against COVID-19, although this does not appear to be strong. Our findings suggest that ice bathing should be considered as an additional means to enhancing the resistance to infection. [ABSTRACT FROM AUTHOR]