The two main risk factors for severe COVID-19 are age and disability.
As you get older you repair less effectivelyand this in part of the aging process. This is in part because your macrophages dont clear the debris as much that is required for remyelination. These cells are going to be less able to get rid of infections. However it is not just macrophages that get old and this can be T cells too.
Immunosenescence: the role of age in multiple sclerosis.Ostolaza Ibáñez A, Corroza Laviñeta J, Ayuso Blanco T.Neurologia. 2020 Sep 19:S0213-4853(20)30226-7. doi: 10.1016/j.nrl.2020.05.016. Online ahead of print.
Introduction: The number of elderly people with multiple sclerosis (MS) has increased in line with population ageing. As the immune system presents profound changes over an individual’s lifetime, it is important to understand the differences between these patients and younger patients.
Development: Immunosenescence, defined as age-related alterations naturally occurring in the immune system, particularly influences tolerance, response, and adverse effects of disease-modifying treatments for MS. Thymic involution (shrinkage of the thymus where new T cells are made) is the most noteworthy characteristic of this phenomenon. This process leads to a reduction in the number of virgin (new naive) T cells. Other effects include an inverted CD4 + /CD8 + cell ratio, severe alterations in NK cell functioning, and reduced tissue repair capacity in the brain.
Conclusions: The number of older people with MS is increasing due to population ageing, advances in disease-modifying treatments, and improved health and social care of these patients. Ageing of the immune system increases the risk of infections, tumours, and autoimmune diseases in elderly individuals. Furthermore, neurodegeneration is accelerated in patients with MS due to the nervous system’s loss of remyelination capacity. Understanding of the changes affecting the immune system in the elderly population is essential to improving the care provided to this ever-growing patient group.