Shortness of air and cough, circulatory problems, fatigue and difficulty concentrating, anxiety and depression. These are just a few of Long Covid symptoms, a new syndrome that some Covid-19 patients (not sure what percentage) carry with them for months after their official recovery.The causes? Still not known exactly, but recently some scientists have put forward an interesting hypothesis: the Long Covid syndrome could be due at least in part to the premature ageing of the immune system (immunosenescence), a consequence of the Sars-Cov-2 infection.The attention of physicians and health systems for this condition is growing a lot, so much so that in the United Kingdom – where it is estimated that there are currently more than one million people with major problems three months after the disappearance of positivity to the virus – the first specialized clinics for Long Covid are emerging.

Long Covid definition

Although we hear a lot about it now, Long Covid remains a condition that has yet to be defined. Mostly, for the time being, Long Covid is referred people who recovered from acute Sars-Cov-2 infection but experience persistent symptoms for more than 4 weeks after disease onset. Not all patients suffer from them (estimates range from 32.6% to 87.4%), but the frequency seems greater the more severe the acute illness was.Long Covid can occur in the:

• lungs, with dyspnea (air hunger), coughing, and hypoxemia;
• circulatory system, with clot formation that can cause pulmonary embolisms and stroke; heart, from palpitations and chest pain to myocarditis and inflammation;
• brain, from migraines to neuropsychiatric symptoms (depression, anxiety, insomnia, post-traumatic stress syndrome, obsessive compulsive disorder), to the so-called brain fog (difficulty in concentrating, memory and language problems, etc);
• kidneys, with renal failure
• nose and mouth, with loss of smell and taste
• hair loss
• joints and muscles, with arthralgia and myalgia
• tiredness (fatigue);
• gastrointestinal system, with diarrheal, acid reflux, loss of appetite, nausea.

Premature aging of the immune system

As New Scientist reports, during the virtual conference of the UK Coronavirus Immunology Consortium and the British Society for Immunology, Niharika Duggal of the University of Birmingham (UK) showed data on 46 patients aged 30 to 68 years who had been hospitalized for moderate and severe forms of Covid-19. Three months after discharge, the immune system of these people had taken on particular characteristics, typical of the over 60s: a decrease in “naive” immune system cells (immature cells, i.e., cells that have not yet been exposed to an antigen), compared with an accumulation of memory B and T lymphocytesLymphocytes are the cells that make up the effective portion of the adaptive immune system; they are able to generate and modify antibodies that will recognize antigens in the future. They are present in primary lymphoid organs, secondary lymphoid organs, peripheral blood and lymph (where they are currently named). and an excess of senescent T lymphocytes. A physiological change after the age of 60 years, called immune-senescence, which, however, can only raise questions if it occurs in young people who survived Covid-19. Il sistema immunitario delle persone ricoverate per Covid-19 appare “invecchiato”

Another study from the Manchester University observed alterations in neutrophil white blood cells, which, even months after official recovery, remain overabundant and nonfunctional. And still research from the Cambridge University found changes in gene expression related to aging of immune system cells in patients who survived Sars-Cov-2.Whether premature aging of the immune system is a cause or a consequence of coronavirus infection is, however, yet to be determined. In other words, the question scientists are asking is: do people with an “old” immune system (regardless of age) get sicker and more severely, or did the virus induce the imbalance? 

Specific data are still limited so it is not possible to draw final conclusions, but according to experts immune-senescence would help to explain several symptoms of Long Covid, for example excessive blood clotting.These implications may seem disturbing, but there is also a positive note: with physical activity and a correct diet, the premature ageing of the immune system does not seem irreversible.