Study reveals surprising risk factors for Covid-19

Since the beginning of the Covid-19 pandemic, SARS-CoV-2 has infected over 600 million people worldwide, resulting in 6.57 million confirmed deaths worldwide – a major underestimate, with studies arguing that this value has already tipped 20 million. Yet, information about factors affecting the probability of infection or experiencing a severe course of the disease remain scarce and often speculative.

Now, a team of researchers led by Charles University in the Czech Republic has surveyed over 30,000 internet users, who shared their information about their exposure to 105 risk factors for Covid-19, including behavioral traits such as taking vitamins and supplements, being actively engaged in sports, keeping pets, swimming in cold water, walking in nature, volunteering, singing, or smoking tobacco or marijuana.

The analysis revealed that people who live in larger cities and have a higher level of education, especially women, had a lower risk of infection, while larger household sizes and the number of children were associated with a higher risk of infection. Moreover, people living on their own had a lower chance of catching Covid-19. 

Quite surprisingly, active involvement in sports, frequent singing, and cold-water swimming increased the risk of infection, while tobacco smoking and marijuana use (in women) had a relatively strong protective effect on both infection and the development of severe illness. However, the most substantial protective factors appeared to be strict adherence to mask-wearing, as well the consumption of vitamins and supplements, particularly vitamin D.

Yet, the most unexpected result was a positive correlation between the severity of disease and adherence to mask wearing and social distancing. The scientists speculate this is because people with comorbidities (such as diabetes, obesity, or chronic respiratory illnesses) tried hard to avoid infection and adhered more strictly to non-pharmaceutical protective measures such as mask-wearing. However, when they did become infected, they often had a more severe course of the disease due to their underlying health factors.

“This preregistered longitudinal study is of explorative nature. Therefore, although the observed effects were strong and remained highly significant even after correction for multiple tests, it will be necessary to confirm their existence in future independent studies,” the authors concluded.

The study is published in the journal Biology Methods and Protocols.

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By Andrei Ionescu, Earth.com Staff Writer

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