Much mystery still surrounds COVID-19 and who it hits hardest.
Some say children may be immune or asymptomatic. Some who contract the virus may require intensive care, while others will experience only mild symptoms or none at all.
Mortality rates suggest a much higher death rate among older people, and yet there are instances of people in their 90s and even centenarians fully recovering from the virus.
However, new research has revealed more about who is most likely to suffer the worst symptoms and who could escape unscathed.
And it seems age is not the dominant factor.
But underlying health conditions are, according to a study of more than 1.3 million COVID cases in the US.
The study, published in the Morbidity and Mortality Weekly Report, revealed that rates of hospitalisation were six times higher for people with underlying conditions compared to those without.
And the death rate was up to 12 times higher.
The most commonly reported underlying conditions were heart disease, diabetes and chronic lung disease. However, other risk factors leading to far more severe COVD-19 outcomes included hypertension, smoking, blood type, obesity, genetic factors and, just as you thought you were getting away with it – age.
Even though underlying conditions are the dominant factor when it comes to severe outcomes, many of these conditions do come with age, says the study.
Around eight in 10 deaths occurred in adults aged 65 or older, says the US Centers for Disease Control and Prevention (CDC).
This is because the likelihood of chronic medical conditions increases significantly with age.
The risk of infection also increases, as immune system efficacy also declines with age, leaving older people more vulnerable to viral infections
While age is still a determining factor when it comes to COVID-19 morbidity, healthy older people are more likely to experience milder symptoms, say the researchers.
The link between chronic disease and the severity of COVID-19 is more about correlation than causation.
The issue of disease variability “is the most critical question about COVID,” Edward Behrens, chief of the rheumatology division at Children’s Hospital of Philadelphia, told the Washington Post.
“Why do some people get sick? Why do some people have no problem at all?”
The ‘why’ is still unclear, although social and demographic factors, (sex, race, ethnicity, income and access to quality healthcare) will all be determining factors on who suffers the most.
Many researchers are in the process of determining personal risk scores – so that someone who has or is vulnerable to COVID-19, could have a better idea of how to manage their lives in the pandemic.
To figure out this risk score, researchers are weighing up the effect of a range of pre-existing conditions, combined with age and other socio-economic factors.
People with diabetes are high on the risk scale, as high blood sugar levels seem to be linked to more severe COVID-19 infections.
Scientists have found that people with diabetes were nearly 3.7 times more likely to have a critical case of COVID-19 or to die from the disease compared to people without any underlying health conditions.
But it may not be diabetes alone that is directly responsible for increasing COVID severity.
Other health conditions associated with diabetes, such as cardiovascular and kidney conditions, could still be to blame.
Flu and pneumonia are also more common and more serious in older diabetics, and the progression of type 2 diabetes has been linked to compromised immune systems, which would lead to poorer outcomes for those exposed to SARS-CoV-2.
However, not all people with type 2 diabetes are at the same risk, as diabetics who keep their blood sugar levels in a tighter range experienced less severe coronavirus symptoms.
People with cardiovascular conditions, such as heart disease and hypertension, also experience worse COVID-19 complications than those with no pre-existing conditions, says the American Heart Association.
A Chinese study of COVID-19 patients found that more than one in five developed heart damage. Some had no pre-existing heart conditions, while others did, leading some scientists to believe COVID-19 might hurt both damaged hearts and healthy ones.
Smokers may also be prone to severe COVID-19 infections, with a heightened risk of developing pneumonia, suffering organ damage and requiring breathing support, says a study published in the New England Journal of Medicine.
In this study, 12.3 per cent of smokers who were admitted to an ICU, were placed on a ventilator or died, as compared with 4.7 per cent of non-smokers.
Several studies suggest a link between obesity and more severe COVID-19 cases. One study found that COVID-19 patients younger than 60 who were obese were twice as likely as non-obese individuals to be hospitalised and were 1.8 times as likely to need critical care.
A Chinese study also found that obese COVID-19 patients were more than twice as likely to develop severe pneumonia compared to those of normal weight.
Even those who are overweight, but not obese, have an 86 per cent higher risk of developing severe pneumonia than people of normal weight, say the study authors.
Scientists also speculate that obesity may increase the risk of severe infection.
Considering that nearly two thirds (67 per cent) of Australian adults were overweight or obese (12.5 million people), this factor has huge implications.
And even if you’re doing everything right, your blood type or genetics may let you down.
Scientists from the Southern University of Science and Technology, Shenzhen, found that people with blood types in the A group (A-positive, A-negative and AB-positive, AB-negative) had a higher risk of contracting the coronavirus compared with non-A group types.
The same study found that those with O blood types (O-negative and O-positive) had a lower risk of getting the infection compared with non-O blood types.
However, scientists are still unsure as to why blood type might increase or decrease the risk of contracting COVID-19.
Somescientists saygenetic factors may also make you more susceptible to the disease, but it seems they are still working on that theory, says a Live Science article.
While all these underlying conditions may make you more susceptible to COVID-19, “the difference between catching COVID and dying is so stark the older you get, it’s important to recognise that,” said Carl Heneghan, director of the Center for Evidence-Based Medicine at Oxford University.
“You have to try and stay healthy, get fit,” he said.
“If you’ve got diabetes, you’ve got to lose weight and moderate that. If you do all those things, your risk of dying is small, or very small.”
What are you doing to improve your health? Could COVID-19 be a wake-up call for you?
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