Covid19 is a disease with very different outcomes within the population, in fact, if fortunately in children it almost always has a slight or asymptomatic outcome, we know that with increasing age the prognosis worsens. Age was immediately identified as a “risk factor” and over the months we realized that other conditions can worsen the course of Covid19. A condition that significantly worsens the prognosis is obesity. Obesity understood as a medical condition in which the BMI is higher than 30 kg / m2 is often accompanied by other comorbidities: hypertension, type 2 diabetes etc.
Why do obese patients have a more severe course?
A recent work published on International Journal of Obesity try to shed some light on this correlation between obesity and Covid19 severity. In this work we studied two patient populations both affected by Covid19, the first (control) group was normal weight while the second was characterized by a BMI greater than 30, i.e. obese.
The researchers studied the level of neutralizing anti-Spike IgG antibodies, they are the antibodies that our system produces to neutralize Sars-CoV2, they are used as an indicator of an adequate response to infection. The obese patients analyzed show a very low quantity of neutralizing antibodies compared to the normal weight patients. This first observation may explain why obese patients have a worse prognosis.
The researchers’ other discovery concerns the presence of autoantibodies. Autoantibodies are antibodies that our body mistakenly forms against its own structures (self). Autoantibodies are involved in many autoimmune diseases where our body attacks itself.
In addition to having few neutralizing antibodies, obese and Covid19 patients also have autoantibodies that can contribute to the severity of the disease.
A potential explanation
It is known that the most serious effects of Covid19 derive from a sort of over-reaction of our immune system which, failing to manage the infection, causes an enormous immune and inflammatory response which in some cases leads to the death of the patient.
Obese patients are subject to a mild persistent systemic inflammation which often remains silent for years but which in case of stimulation can worsen in a short time. The authors of the article hypothesize that this mild state of systemic inflammation that characterizes obese subjects could result in a particularly violent autoimmune reaction in case of Sars-CoV2 infection.
In practice, it is as if a lot of flammable material accumulates inside obese subjects and the Sars-CoV2 infection represents an open flame that triggers a very violent fire.
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Take home messages:
1) obese subjects are more at risk of developing a severe form of Covid19
2) obesity often manifests itself with other pathologies and conditions such as diabetes and hypertension, also these risk factors for Covid19
3) the study is relatively small and published in a modest journal so we await further confirmation from other journals and on larger samples
4) the goal of works like this is to build a sort of predictor model that can indicate with relative certainty who will suffer the worst consequences from a Sars-CoV2 infection
5) this work reaffirms the importance for people at risk, such as the obese, to get vaccinated in order to have a more robust immune response
Aureliano Stingi, doctor in molecular biology works in the field of precision oncology. Collaborate with the World Health Organization in the battle against Covid19-themed fake news