The research, based on 17,000 COVID-19 admissions, revealed that overall a third of Britons hospitalised with the life-threatening virus die.
Death rates were 37 per cent higher among obese patients, second only to dementia (39 per cent) but more than heart disease (31 per cent).
Heart disease was also found to be the most common underlying health condition in coronavirus patients hospitalised with the infection.
The study, considered to be the largest of its kind in Europe, revealed more than half (53 per cent) of patients had at least one comorbidity.
Almost a third (29 per cent) had heart disease – conditions which block blood vessels and make it hard to pump blood and oxygen around the body.
Nearly a fifth (19 per cent) were diabetic, the same number had lung disease, 15 per cent suffered from kidney disease and 14 per cent were asthmatic.
Curiously, fewer than 10 per cent of hospital admissions were smokers – more than a third less than the national rate of 14.4 per cent.
It is the latest in a growing line of studies to suggest that cigarette users may have a lower risk of becoming seriously ill with COVID-19.
Researchers are struggling to knock down an apparent protective effect given by cigarettes, which they’ve described as ‘weird’.
Researchers analysing almost 17,000 COVID-19 admissions found more than half (53 per cent) had at least one comorbidity. The most common was heart disease (29 per cent), diabetes (19 per cent), lung disease (19 per cent) kidney disease (15 per cent) and asthma (14 per cent)
Curiously, fewer than 10 per cent of hospital admissions were smokers – more than a third less than the national rate of 14.4 per cent (stock image)
A third of coronavirus patients admitted to NHS hospitals die from the disease, the biggest COVID-19 study in Europe shows
Researchers analysing almost 17,000 COVID-19 hospitalisations in the UK found 49 per cent were discharged
The report by the International Severe Acute Respiratory and emerging Infections (ISARIC) also found 17 per cent of patients admitted to hospital are still receiving care
The bleak realities of the crisis were laid bare in a report by the International Severe Acute Respiratory and emerging Infections (ISARIC).
It was conducted by a team of Britain’s top infectious diseases scientists who are part of the pandemic-planning global body.
The research looked at 16,749 admissions between February 6 and April 18 at hospitals in England, Scotland and Wales.
Although COVID-19 is a respiratory disease that primarily affects the lungs, the body comes under enormous stress while trying to fight back.
Those who have underlying conditions ‘have less of a safety net’ to cope with the demands, Professor Naveed Sattar, an honorary consultant in cardiovascular and medical sciences, explained.
He told MailOnline: ‘If you are healthy, your buffer capacity is good. The rest of your body can cope with the stress.
WHAT IS AN ACE-2 RECEPTOR AND WHAT DOES IT HAVE TO DO WITH COVID-19?
ACE-2 receptors are structures found on the surface of cells in the lungs and airways which work with an enyzme called ACE (angiotensin-converting enzyme) to regulate blood pressure.
Its exact function in the lungs is not well understood but studies suggest it is protective against lung damage and low levels of it can worsen the impact of viral infections.
Scientists say that the coronavirus which causes COVID-19 enters the body through the ACE-2 receptor, which the shape of it allows it to latch on to.
This means that someone with more ACE-2 receptors may be more susceptible to a large viral load – first infectious dose of a virus – entering their bloodstream.
ACE-2 receptors have a shape which matches the outside of the coronavirus, effectively providing it with a doorway into the bloodstream, scientists say
People who have higher than usual numbers of ACE-2 receptors may include those with diabetes or high blood pressure because they have genetic defects which make them produce more. Emerging evidence shows that smokers may also produce more.
High levels of ACE-2 receptors may also be protective, however.
They are thought to be able to protect the lungs during infection and a study on mice in 2008 found that mice which had ACE-2 blocked in their bodies suffered more damage when they were infected with SARS, which is almost identical to COVID-19.
Smoking has in the past been repeatedly linked to lower than normal levels of ACE-2 receptors, potentially increasing the risk of lung damage from COVID-19.
‘But if you have impairments to begin with, your systems break down.’
In many patients with COVID-19, the lungs are unable to receive enough oxygen. This has a knock-on effect on other organs.
Professor Sattar, at the University of Glasgow, explained the heart comes under a lot of strain trying to pump oxygenated blood around the body, including to the brain.
Dr Hajira Dambha-Miller, a GP and clinical lecturer, said the blood is less able to circulate in people who have high blood pressure because their vessels are narrower.
Not only does this slow the route of oxygen to organs, but it also means immune cells in the blood are not able to reach the virus as quickly as needed.
‘If you’ve got diabetes’, she said, ‘you have high sugar levels and your blood becomes like treacle.
‘Physically, its harder for the immune system to get to the virus. The virus bugs do a lot of damage before the immune system even realises it’s there.
‘When the body does kick in, it won’t work as it should do. The immune cells are damaged because they’ve been saturated in sugar for years and don’t work the way they should.’
The ISARIC study is the latest to suggest smokers are at less risk of falling seriously ill with coronavirus.
University College London academics looked at 28 papers and found the proportions of smokers among hospital patients were ‘lower than expected’.
One of the studies showed that in the UK the proportion of smokers among COVID-19 patients was just five per cent, a third of the national rate of 14.4 per cent.
Another found in France the rate was four times lower. In China, a study noted 3.8 per cent of patients were smokers – despite more than half of the population regularly smoking cigarettes.
Commenting on the matter, Linda Bauld, a professor of public health at the University of Edinburgh, said ‘there’s something weird going on with smoking and coronavirus’.
Professor Bauld said the way the virus enters the body may be blocked by effects of nicotine – the addictive compound found in tobacco.
The coronavirus enters cells inside the body via structures called ACE-2 receptors, which coat the surface of some cells, including in the airways and lungs.
The numbers of ACE-2 receptors someone has are thought to vary depending on genetics and some evidence suggests that they are higher in smokers.
This could, in theory, put them at a higher risk of contracting the coronavirus.
However, the virus is known to cause lung damage by depleting the numbers of ACE-2 receptors, so the fact that smoking increases them could reverse the effect and prevent harm to the lungs.
On the other hand, other studies show that nicotine reduces the action of the ACE-2 receptor, suggesting smokers are less likely to catch the virus in the first place.
Some experts say hospitals are probably not recording patients’ smoking status properly, potentially because they are too busy, patients are too sick to answer, or because people lie in their answers.
But for the latest study, smoking was the only co-morbidity researchers had a full set of data to analyse.
The ISARIC study also found a third of coronavirus patients admitted to NHS hospitals die from the disease and more than half of those on ventilators do not survive.
Of those admitted to general wards, 33 per cent died, 49 per cent were discharged and 17 per cent are still receiving care.
The study showed only a fifth of intubated UK patients made it home alive. Fifty-three per cent have died while on a ventilator and 27 per cent are still hooked up to the machines at the time of writing.
Of those in ICU, 45 per cent succumbed to the virus, 31 per cent went home after beating the illness and just under a quarter are still being treated.