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Smoking DOES increase the risk of catching coronavirus, study of 2.4million British people finds

Smoking does increase the risk of getting coronavirus, according to a major British study that disputes growing evidence that the habit is protective.

A team at Imperial College London looked at 2.4million Britons, of which 11 per cent reported smoking.

All participants were users of the COVID Symptom Study app, which asks people to regularly report their health and if they have symptoms of the coronavirus, helping to build a clearer picture of the UK’s outbreak.

Current smokers were 14 per cent more likely to develop tell-tale symptoms, such as a persistent cough and high temperature, suggesting a diagnosis of COVID-19. 

They were also 50 per cent more likely to suffer other symptoms, such as diarrhoea, loss of appetite and delirium. 

In addition, current smokers who tested positive were more than twice as likely to need to attend hospital due to COVID-19.

Smokers are known to be at higher risk of catching other viruses because they touch their mouth more and the potent chemicals damage airways. 

Mounting evidence has suggested smokers are at less risk of COVID-19 but are more likely to get severely sick if they catch it.

Researchers across the world have discovered very low numbers of smokers among hospitalised COVID-19 patients, suggesting they are protected.

But the data has been full of holes because doctors are not always able to find out if someone severely sick is a smoker. 

It’s left scientists split on the topic, with some so convinced smoking is protective against COVID-19 they are planning to trial nicotine patches as a preventative tool. 

Smoking does increase the risk of catching the coronavirus, according to a British study, throwing out the theory the habit is protective

Smoking does increase the risk of catching the coronavirus, according to a British study, throwing out the theory the habit is protective

Smoking does increase the risk of catching the coronavirus, according to a British study, throwing out the theory the habit is protective 

It comes after a string of studies have shown  a surprisingly low prevalence of smokers in COVID-19 hospital patients. The graph shows the smoking rate of each country against the percentage of smokers among COVID-19 patients, as reported by a review of studies by University College London. The lowest figure has been chosen for each country to show the stark comparison discovered by some studies

It comes after a string of studies have shown  a surprisingly low prevalence of smokers in COVID-19 hospital patients. The graph shows the smoking rate of each country against the percentage of smokers among COVID-19 patients, as reported by a review of studies by University College London. The lowest figure has been chosen for each country to show the stark comparison discovered by some studies

It comes after a string of studies have shown  a surprisingly low prevalence of smokers in COVID-19 hospital patients. The graph shows the smoking rate of each country against the percentage of smokers among COVID-19 patients, as reported by a review of studies by University College London. The lowest figure has been chosen for each country to show the stark comparison discovered by some studies 

A review of 28 studies by University College London in April found a ‘lower than expected’ rate of smokers among COVID-19 patients.  

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.   

WHY MAY SMOKERS BE MORE AT RISK OF SEVERE CORONAVIRUS? 

Dr James Gill, a locum GP and honorary clinical lecturer, Warwick Medical School, said: ‘Smoking is a significant risk factor for coronavirus infections and, in fact, infections generally. 

‘There are many interlocking factors as to why smoking reduces the body’s ability to fight an infection.

‘Possibly one of the biggest reasons smokers are at increased risk of respiratory infections is the impairment and death of the cilia in the airways and lungs.

‘In simple terms, the airways are lined with cilia – small brush-like hairs – these structures provide an absolutely vital function in moving mucous, inhaled debris and potentially infectious agents out of the airways and lungs before an infection can take hold.’

Increased levels of carbon monoxide in the blood, a by-product of smoking, blocks the blood’s ability to carry oxygen to cells in the body.

It puts smokers at a pre-disposed disadvantage if they catch coronavirus, considering the disease leaves patients unable to get enough oxygen into the bloodstream due to lung inflammation.

Dr Tom Wingfield, a senior clinical lecturer and honorary consultant physician, Liverpool School of Tropical Medicine (LSTM), said: ‘Smoking both increases someone’s vulnerability to infection (repetitive touching of hand-to-face and hand-to-mouth) and reduces their ability to fight against it resulting in more severe disease.’

He highlighted the tendency of smokers to have a health condition, such as high blood pressure, high disease and chronic lung, ‘all of which themselves are risk factors for severe COVID-19’.

Professor Gordon Dougan, department of medicine, University of Cambridge, said: ‘The real danger lies in the lung and systems damage COVID causes. It will make people more vulnerable to secondary bacterial and viral infections. It is known that lung damage per say does that.’ 

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But researchers have often noted that low prevalence of smokers may just be because doctors are just too busy to be accurately noting down everyone’s smoking habits, or patients are too unwell to speak. 

Considering elderly people are more likely to be hospitalised with COVID-19, low smoking rates may be explained by differences in smoking rates in different age groups, with middle-aged people more likely to have the habit. 

There is often data missing in these studies too, which could skew results.

The team at Imperial College London, led by Dr Nicholas Hopkinson, have taken a different approach to the majority of studies so far which used hospital data.

They used information from the COVID-19 Symptom app, which was developed by King’s College London to help track the crisis.

More than 3.6million people in the UK have downloaded the app since March. 

On first use, the app records self-reported location, age, and core health risk factors, including height, weight, smoking and common disease. 

Users are told to regularly report their health and if they develop symptoms of the coronavirus – up to 14 – and the results of a test if they get one.

For this study, the researchers took data from 2.4million who had entered data via the app between 24th March and 23rd April 2020.

Some 11 per cent of the group were smokers. The researchers said this may  be lower than the national average (14 per cent) because wealthier people are less likely to smoker while also be more likely to have a smartphone. 

The main finding was that current smoking was linked with a ‘substantially increased risk of developing symptoms suggestive of COVID-19’.  

Among ‘standard users’ – those who never actually had a test – current smokers were 14 per cent more likely to develop the classic triad of symptoms of COVID-19 than non-smokers.

These were a fever, persistent cough and shortness of breath.

They were also 29 per cent more likely to have more than five symptoms, and 50 per cent more likely to have more than 10 symptoms.

Doctors at The Royal Glamorgan Hospital are currently waiting for funding and ethical approval to move forward with a trial of nicotine patches to prevent COVID-19

Doctors at The Royal Glamorgan Hospital are currently waiting for funding and ethical approval to move forward with a trial of nicotine patches to prevent COVID-19

Doctors at The Royal Glamorgan Hospital are currently waiting for funding and ethical approval to move forward with a trial of nicotine patches to prevent COVID-19

WHY IS SMOKING THOUGHT TO PROTECT AGAINST THE CORONAVIRUS? 

Swathes of studies have shown a low prevalence of smokers in hospitals with COVID-19. 

When smokers do get diagnosed with the virus, however, they appear to be more likely to get so sick that they need ventilation, two studies in the review showed. 

If the findings are proven, scientists say it’s likely that it is not cigarettes – filled with thousands of harmful chemicals – that would offer a potential protection, but the nicotine that is beneficial. 

A theory flouted by scientists is that nicotine reduces ACE-2 receptors, which are proteins in the body the virus binds to in order to infect cells.

The coronavirus enters cells inside the body via the structures, which coat the surface of some cells, including in the airways and lungs.   

If nicotine does lowers ACE-2 expression, it makes it harder for viral particles to gain entry into cells and therefore cause an infection.  

On the other hand, other studies show that nicotine enhances the action of the ACE-2 receptor, which in theory, puts smokers at a higher risk of contracting the coronavirus.  

Other scientists say low levels of ACE-2 expression as a result of nicotine may prevent worse damage from viral infection, and there is no evidence that says higher quantities of ACE-2 receptors increases the risk of SARS-CoV-2 infection in the first place.

Dr Konstantinos Farsalinos, from the University of West Attica, Greece, who queried whether nicotine could be a cure for COVID-19 in a paper published on May 9, said: ‘Up-regulation of ACE2, though seemingly paradoxical, may in fact protect patients from severe disease and lung injury.’ 

A 2008 study in mice found that getting rid of ACE-2 made the animals more likely to suffer severe breathing difficulties when infected with the SARS virus, which is almost identical to COVID-19.   

Other scientists have turned their head towards nicotine’s ability to prevent inflammation, where evidence is more robust.  

Nicotine has been shown inhibit the production of pro-inflammatory cytokines, such as TNF, IL-1 and IL-6, which are involved in promoting an inflammatory response. 

A ‘cytokine storm’ is a phenomenon in which an abundance of cytokines are released in response to infection.   

Doctors have previously said that it’s often the body’s response to the virus, rather than the virus itself, that plays a major role in how sick a person gets. 

A cytokine storm can lead to respiratory failure and the attack of healthy tissues, causing multi-organ failure. 

Therefore, the cytokine storm is being looked at as a target for COVID-19 treatment.  

‘Nicotine has effects on the immune system that could be beneficial in reducing the intensity of the cytokine storm,’ Dr Farsalinos wrote in Internal and Emergency Medicine.

‘The potential benefits of nicotine…. could explain, at least in part, the increased severity or adverse outcome among smokers hospitalized for COVID-19 since these patients inevitably experience abrupt cessation of nicotine intake during hospitalization.

‘This may be feasible through repurposing already approved pharmaceutical nicotine products such as nicotine patches.’ 

Dr Nicola Gaibazzi, who recently published findings on MedRxiv of ‘very low’ numbers of smokers in Italian COVID-19 patients, speculates smoke exposure may bolster the immune system.

He said exposure to cigarette smoke reduces the body’s immune system over time, measured by lower inflammatory markers. 

Therefore, when smokers are infected with a virus like SARS-CoV-2, their immune system is more ‘tolerant’ and does not overreact. 

On the other hand, non-smokers may be more prone to having the sudden and deadly cytokine storm when they are infected with the virus.  

Scientists have stressed that the evidence supporting nicotine as a medicine does not mean everyone should take up smoking. 

These included abdominal pain, chest pain, delirium, diarrhoea, fatigue, headache, hoarse voice, loss of smell, skipped meals, sore throat and unusual muscle pains.

The researchers said this indicated their disease was more severe because those that reported going to hospital tended to have more symptoms. 

The study then looked at people who had actually received a test result for COVID-19, where results differed slightly. 

They first pointed out that smoking prevalence was two per cent lower in the group that got tested compared to those who did not. 

This, they said, was because healthcare workers are more likely to get a test, but also less likely to be smokers. 

Due to testing limitations in the UK, only healthcare workers or people in hospital were able to get a test at that time. 

There were less smokers in the group who tested positive than negative (7.4 per cent vs 9.3 per cent), suggesting smoking is protective.

However, the researchers said smokers were more worse affected.

People with a positive result were 42 per cent more likely to have more than 10 symptoms, suggesting they suffered more than their non-smoker counterparts.

In addition, current smokers who tested positive were more than twice as likely to need to attend hospital due to COVID-19.

This risk only dropped marginally when pre-existing health conditions were taken into account. 

The findings are in stark contrast to smaller and less accurate papers so far, citing a lower risk of hospitalisation in smokers.  

The authors concluded in their pre-print paper, which has not been peer reviewed by other scientists: ‘Our results provide compelling evidence for an association between current smoking and individual risk from COVID-19, including symptom burden and risk of attending hospital.’

In light of emerging evidence that smokers make up low numbers of hospital patients, scientists have discussed how nicotine affects the expression of ACE-2 receptors.

ACE-2 are proteins in the body the virus binds to in order to infect cells.  

If nicotine does lowers ACE-2 expression, it makes it harder for viral particles to gain entry into cells and therefore cause an infection. 

But if it enhances ACE-2 receptors, in theory, this puts smokers at higher risks of catching the coronavirus. 

To put this to bed, the Imperial team measured ACE2 expression in adipose tissue, which is made of fat cells.

The samples came from 541 women including 54 smokers, 196 past smokers and 291 non-smokers. 

Smokers were found to have reduced ACE2 expression in adipose tissue compared to non-smokers. 

This would suggest smokers are less likely to catch the coronavirus. However, the research in this area is so vague it is difficult to say whether this is the case.

Even Dr Hopkinson and colleagues wrote the matter was ‘complicated’.  

What is more clear, is that lower numbers of ACE-2 receptors appear to exacerbate the disease because they are protective against lung injury. 

The virus itself is known to cause lung damage by depleting the numbers of ACE-2 receptors. Therefore, if nicotine reduces ACE-2 receptors, this would make matters even worse.

But on the other hand, if nicotine boosts ACE-2 receptors, as suggested by other research, withdrawal from it during a hospital stay would also potentially lead to worse outcomes. 

Studies have shown nicotine may prevent a severe over-reaction of the immune system called a cytokine storm – a phenomenon found to be killing many COVID-19 patients. 

Welsh NHS doctors who want to do COVID-19 trials with medicinal nicotine patches based on the theory the addictive chemical is protective in some way.

Doctors at The Royal Glamorgan Hospital are currently waiting for funding and ethical approval to move forward with a trial of some kind. 

Researchers in France are also planning a trial after finding low levels of smokers in a hospital in Paris.

The move would be controversial, considering studies such as that by Imperial warn smoking is a risk factor for COVID-19. 

WHAT HAVE STUDIES IN EACH COUNTRY SHOWN? 

Italy

A recent Italian study found fewer than five per cent of 441 COVID-19 patients who needed to be admitted to an Italian hospital were smokers.

The scientists described it as a ‘very low’ number, given that a quarter of the general population are known to be hooked on cigarettes.  

The Italian study led by Dr Nicola Gaibazzi looked at patients admitted to hospital in Parma, Northern Italy.  

It means the findings can only be applied to those with symptoms severe enough to seek medical attention – thousands of patients escape suffering any symptoms. 

Information about smoking was taken from medical records, and efforts were made to directly contact the patients or their relatives for confirmation. 

Previous research on the topic has been full of holes because researchers admit data had been missing. 

But in this study, a total of 423 out of 441 patients or their relatives were spoken to on the phone, which strengthens the data.  

Non-smokers made up 85 per cent of deaths, smokers 6 per cent and ex-smokers 9 per cent – which was not significantly different to the total cohort.

However, active smokers had a 50/50 chance of survival once hospitalised – 47 per cent of those admitted died. In comparison, just over a third of non-smokers died.

China  

The UCL review included 22 studies conducted in hospitals in China, which showed that 3.8 to 17.6 per cent of COVID-19 patients were current smokers and fewer than five per cent were former smokers. 

However, 2018 data shows more than half the population of the country are current smokers (50.5 per cent of men and 2.1 per cent of women).  

And almost one in 10 of non-smokers in China are former smokers (8.4 per cent of men and 0.8 per of women).

A separate study published in early April by scientists in New York and Athens looked at 13 Chinese studies that had registered smoking as a precondition and found that the number of smokers across the whole sample of 5,300 patients was 6.5 per cent. 

It’s an astonishingly small number in country where half of all men still smoke. 

South Korea 

In one South Korean study looked at by UCL, 18.5 per cent were current smokers, which almost matches the smoking prevalence of 19.3 per cent in 2016.

France 

In a study conducted in France, 7.1 per cent were current smokers, 6.1 per cent of whom were hospitalised. But much higher smoking rates are recorded in the population –  32 per cent.

However the results were different for former smokers, of which there are 31.4 per cent in France. A much higher 59.1 per cent of COVID-19 patients were former smokers. 

UK 

In the international study with participants predominantly from the UK in a hospital setting, five per cent were current or former smokers. 

This compares with a current and former smoking prevalence of 14.4 and 25.8 per cent in England in 2018, ‘suggesting a lower than expected proportion of current and former smokers in the included study’. 

US 

One study conducted by America’s Centers for Disease Control of over 7,000 people who tested positive for coronavirus, found that just 1.3 per cent of them were smokers – against the 14 per cent of all Americans that the CDC says smoke.

The study also found that the smokers stood no greater chance of ending up in hospital or an ICU. 

In US studies reviewed by UCL, 1.3 to 27.2 per cent were current smokers, in contrast to a smoking prevalence of 13.8 per cent in 2018.

And 2.3 to 30.6 per cent were former smokers, compared with the 20.9 per cent of former smokers across the states.

Similarly, data published in the The New England Journal of Medicine from New York City, the epicentre of the US epidemic, shows just 5.1 per cent of patients are smokers.    

Source: dailymail US

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