Since the beginning of the pandemic, it has been clear that Covid19 affects the elderly harder. The greatest number of deaths was in fact recorded in the population over 70 years of age. A new work today sheds light on a possible explanation for why older people are more vulnerable to the disease.
The elderly most affected by Covid, the hypotheses
Currently there is no univocal explanation of the reasons why elderly people are most affected by severe Covid19: in fact, there are a number of elements that contribute to this trend.
There are biological reasons that make elderly subjects more susceptible to Covid19: in order to enter our cells, Sars-CoV2 uses the ACE2 receptor, a particular “gateway” which is much more expressed in elderly subjects than in young people. Furthermore, elderly subjects produce greater quantities of a protein (CHI3L1) which appears to facilitate the entry of Sars-CoV2 into cells.
The role of comorbidities
In addition to the specific biological characteristics, there are also general elements that characterize the elderly: for example, they are characterized by comorbidities, as it is not uncommon for a person over the age of seventy to present at least two or three pathologies. By pathologies we also mean syndromes or conditions that today are totally kept under control through drugs, such as mild hypertension, type 2 diabetes, obesity, cardiovascular problems, systemic inflammation, etc.
Although the symptoms of these diseases are kept at bay by drugs, they contribute significantly to life expectancy. As comorbidities increase, the likelihood of death increases. We know that Covid19 is more severe in obese, hypertensive and diabetic subjects, which precisely characterize the elderly more often.
The aging of the immune system
Finally, one of the most important elements to consider when analyzing why the elderly are more prone to Covid19 is that the immune system, like any other organ or apparatus in our body, ages with increasing age, losing its effectiveness and potency. .
In the elderly, all organs function less efficiently (just think of sight and hearing or the elasticity of the joints or the ability to recover after trauma) and the immune system is not exempt from such a mechanism.
It is not uncommon for a “simple” flu or bacterial infection to be lethal in an elderly subject, while the same identical pathologies in a young and immunocompetent subject would be easily manageable and eliminated.
Antibodies and T lymphocytes
But if, on the one hand, the antibody response in the elderly is comparable to that of young subjects, the real difference is in the cell-mediated response, i.e. the one carried out by T lymphocytes. We have learned that T lymphocytes fight alongside antibodies to eliminate infections. and viruses. During the Covid19 pandemic we often focused only on the antibody response: we constantly wanted to know our antibody level by carrying out serological tests but we forgot the other armed arm of our immune system, the T lymphocytes.
In a work published a few weeks ago, the researchers focused on the cell-mediated response carried out by T lymphocytes in elderly subjects and realized that the repertoire of T lymphocytes is significantly reduced compared to young subjects.
In practice, the elderly produce qualitatively fewer T lymphocytes against Sars-CoV2 and are therefore less protected from the contraction of a severe and highly symptomatic disease.
Obviously this is only an element that is added to those previously listed but which tries to provide a further explanation of why elderly subjects on average experience a more severe form of Covid19.
TAKE HOME MESSAGE:
- elderly subjects are more predisposed to developing severe forms of Covid19
- the immune system becomes less efficient and powerful over the years
- elderly subjects produce a smaller repertoire of T lymphocytes than young subjects
- T lymphocytes play a key role in preventing symptomatic and severe disease
Aureliano Stingi, doctor in molecular biology, works in the field of precision oncology. He collaborates with the World Health Organization in the battle against Covid19-themed fake news