Why are older people more at risk from coronavirus?

Dr Elizabeth Webb, Senior Research Manager at Age UK, has an MSc in Epidemiology from the London School of Hygiene and Tropical Medicine and a PhD in Social Epidemiology from University College London. She discusses that while there’s evidence to support older people being more likely to be hospitalised, or even die, as a result of coronavirus (COVID-19), it’s still unclear why this is.

Coronavirus and its impact on different people

Over the past few weeks, there’s been a lot of focus on the scientific evidence the Government has used to inform their guidance on social distancing, self-isolation and shielding. This branch of epidemiology uses mathematical modelling to predict the progress of coronavirus, combining what we know about the virus and how it spreads, with how people behave.

However, in the background, there is another branch of epidemiology that helps us understand how coronavirus might impact upon people, dependent on their own specific characteristics and risk factors, such as age. This type of epidemiology – observational epidemiology – not only informs our predictions of how the epidemic will progress through the population, but helps us understand how coronavirus might affect certain groups of the population differently, and helps doctors decide which treatments might work best for different people.

Not everyone responds to coronavirus in the same way, and observational epidemiology aims to help us understand why. Information on large numbers of people with coronavirus is collected and used in statistical models to understand how and why experiences vary. Information collected includes background characteristics, or risk factors such as age, sex and pre-existing illnesses, as well as information on what happens to people once they have coronavirus, referred to as outcomes.

It's difficult to get the data

But there are limited resources for collecting this sort of data. Ideally, we would like to have detailed information on a sample of members of a community, but as this hasn’t been possible yet, the coronavirus studies rely on looking at what happens to people who are unwell enough to go to hospital. This relies on doctors having to collect epidemiological data on their patients while treating them.

The emerging observational studies help us start to understand who suffers most from coronavirus. In one such study, researchers in Wuhan, the city in China where the pandemic began, used information they collected on 191 patients with coronavirus in two hospitals in the city. This information was then used in multivariable models – in which the relationships between many risk factors and an outcome can be considered together – to compare the characteristics of the people who were discharged from hospital, and the people who sadly died.

Emerging evidence

The researchers found some evidence that certain pre-existing conditions, including coronary heart disease, Chronic Obstructive Pulmonary Disease (COPD), diabetes and hypertension, were linked to higher chances of dying of coronavirus. They also showed that there was a relationship between age and the risk of dying, regardless of any pre-existing conditions. For each year older the patient was, they had about a higher risk of dying from coronavirus. This evidence is supported by other studies from China and Italy that show increased risk of dying from coronavirus among older people.

So even though the science is still developing, the available evidence supports the notion that older people are more at risk of coronavirus and should be following the Government’s guidance about social distancing particularly carefully and consider whether they need to go outside at all.