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Ageing and COVID-19
Why are the elderly vulnerable to COVID-19?
Age and comorbidities are major risk factors for severe COVID-19. The importance of maintaining health in old age is highlighted by the disastrous consequences of the ongoing COVID-19 pandemic on the elderly. But why is ageing a major factor?
The COVID-19 pandemic is sweeping across the UK and world. Older adults and people with comorbidities are at higher risk of getting seriously ill and dying from COVID-19. People with COVID-19 can be divided into three groups: people that do not have any symptoms, people with milder symptoms who do not require hospitalisation and people with severe respiratory symptoms and high viral load. One of the biggest unanswered questions is why some develop severe disease, whilst others do not. The current understanding is that age, frailty, chronic disease and physiological factors all play a role.
Ageing of the immune system
In general, the infection triggers a robust primary immune response in younger adults, which clears the infection. A sort of memory is also formed so that the immune response is triggered quickly if there are later infections. In older adults the initial immune response is less robust, there is incomplete clearance of the infection and also the recall is less robust. This is because as the immune system undergoes dramatic age-related changes. As the immune system ages, it declines to a state of immunosenescence, where it loses the ability to protect against infections. Vaccine responses are also typically impaired in older individuals because of this inability to respond.
Another important aspect of ageing is that other parts the immune system become overactive. Inflammatory responses mediated by the innate immune system gain in intensity and duration, making older individuals susceptible to tissue-damaging immunity and inflammatory disease.
Cytokine storm: the body’s response to infection goes into overdrive
The decreased ability to respond to pathogens in combination with an overactive inflammatory response seems to play a particularly important role in people who get seriously ill with Covid-19. Initially the virus spreads more easily, causing damage to the cells infected by the virus, in particular cells in the respiratory tract. The damaged cells release a form of signalling molecules called cytokines, triggering an inflammatory response.
In some patients, excessive or uncontrolled levels of cytokines are released which then activate more immune cells, resulting in hyperinflammation. This can seriously harm or even kill the patient and this overreaction of the body’s immune system is called a cytokine storm.
The sudden crash in patients with COVID-19
The cytokine storm is a runaway response that can cause more damage to the body’s own cells than to the virus it’s trying to defeat, and is thought to be the main reason for why patients can very rapidly deteriorate. Cytokine storms might explain why some people have a severe reaction to COVID-19 while others only experience mild symptoms
If the air sacs, that is tiny extensions of the lungs where oxygen is being absorbed and carbon dioxide released, become inflamed, there is an outpour of inflammatory material [fluid and inflammatory cells] into the lungs and we end up with pneumonia (inflammation of the lungs). Lungs that become filled with inflammatory material are unable to get enough oxygen to the bloodstream, reducing the body’s ability to take on oxygen and get rid of carbon dioxide. This is the usual cause of death in Covid-19 patients with severe pneumonia.
The importance of healthy ageing for fighting infectious diseases
Ageing is characterised by universal processes that can be observed across individuals and species. These processes contribute to immune ageing and chronic inflammation, which might explain why the elderly are vulnerable to COVID-19.
In addition, chronic illnesses increase the risk of severe COVID-19. Studies show that additional diseases are present in many patients, obesity, hypertension diabetes and coronary heart disease being common. These are all age-related, inflammatory diseases, and are likely to contribute to vulnerability to COVID-19.
To improve the ability of the population to respond appropriately to COVID-19 and other infections, it is important that we improve overall health and decreased chronic, age-related diseases. By targeting ageing we can make the body more resilient and able to withstand infections.
2020-2030 – The Decade of Healthy Ageing?
Ageing is typically accompanied by a number of chronic diseases, affecting the quality of life for the elderly but also having a huge impact on wider society. The importance of improving the way we age and age more healthily has been acknowledged by agencies and governments globally, who have recognised the challenges that ageing poses to healthcare systems around the world. The WHO is dedicating 2020-2030 to the Decade of Healthy Ageing with the aim of developing strategies to tackle the ageing challenge. The handling of COVID-19 and how we prepare for future pandemics will be an important part of this effort.
Webinar on how ageing research can protect against COVID-19
Watch this webinar hosted by the American Federation on Aging Research on how ageing research can help sustain older adults’ immune health, and protect against COVID-19.
Webinar on how altered immunity during ageing affects SARS-CoV-2 infection
The British Society of Immunology is hosting a webinar series on COVID-19 research. Watch the first webinar on The impact of altered immunity during ageing on SARS-CoV-2 (COVID-19) infection by Prof Arne Akbar, University College London:
The entire series can be found here.
The Buck Institute series on the biology of ageing and COVID-19
The Buck Institute in California is a research institute focusing on understanding the biology of ageing and now conducting research on ageing and COVID-19. Watch their discussions on the COVID-19 pandemic here.
Read about the potential of ageing treatments to treat COVID-19
Read Alex Zhavoronkov’s piece in Aging Journal on why existing ageing strategies should be tested to treat COVID-19 and other infections affecting the elderly.