Although the Covid-19 pandemic has affected the entire globe, the number of infections and deaths is unevenly distributed between geographical regions, and the risks of severe infections is extremely variable from individual to individual. Better understanding why some people develop asymptomatic infections, while others lose their lives is crucial for finding reliable treatments and controlling the pandemic.
Now, a team of scientists from Eötvös Loránd University (ELTE) in Hungary has examined over one thousand studies about risk factors for Covid-19 in order to understand how demographic factors (age, gender), the interaction of the coronavirus with other infectious and non-communicable comorbidities, genetic polymorphisms, lifestyle, gut microbiota, established immune memory, genetic variations in the coronavirus, or environmental factors such as air pollution and socioeconomic factors influence the severity of Covid.
The analysis revealed that advanced age is among the strongest risk factors for Covid-related mortality, with the risk of death in adults doubling approximately every six to seven years of life. According to the experts, aging of lung tissue and the immune system, together with age-related increases in sterile systemic inflammation levels may be responsible for this phenomenon.
In the case of comorbidities, the scientists discovered that, although some chronic diseases such as obesity, diabetes, hypertension, chronic kidney disease, or cardiovascular issues are clear risk factors, the impact of various immunological, neurological, or mental diseases is still unknown. Even in the case of lung diseases, the scientists observed controversial cases. For instance, while chronic obstructive pulmonary disease has an aggravating effect on Covid-19 infections, allergic asthma has been found to be a neutral or even risk-reducing underlying condition.
Current data also shows that men are twice at risk of developing severe Covid-19 than women (regardless of age) – most likely due to differences in genes that play a key role in the immune system – but women have greater chances of struggling with long-Covid symptoms after the acute phase of the infection. Moreover, pregnant women who are infected with the coronavirus are at high risk of developing gestational hypertension, and are more frequently admitted to intensive care.
Many studies have also focused on the indirect effects of the environment, with poor socioeconomic status, poor housing conditions, or belonging to ethnic minorities often leading to more severe disease outcomes. While regular physical activity and a healthy diet are important for strengthening the immune system and mitigating the effects of SARS-CoV-2, poor nutrition and exposure to air pollution or other infectious respiratory diseases can lead to more severe infections. Finally, although alcohol consumption was found to increase the risk of severe Covid-19, the impact of smoking is still highly debated.
“Awareness of these factors can help decisions in the clinic (whom to treat, how to allocate resources), and also public health decisions at the population level. While prevalent immunity from previous infections and vaccinations (and the emergence of the Omicron variants) has substantially reduced the overall risk of severe outcomes compared with the first waves of the pandemic, the risk factors identified in previous analyses are likely to continue to shape relative risks in the future,” the authors concluded.
The study is published in the journal Viruses.
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