RECENT media reports have sensationally and misleadingly suggested that smoking may paradoxically have a protective effect against the severe acute respiratory syndrome SARS CoV-2 coronavirus and that smokers are less likely than non-smokers to fall ill and suffer severely from Covid-19.
This tenuous assumption is based on global data that curiously showed a remarkably low proportion of smokers amongst hospitalized Covid-19 patients in China, the US and France.
Smokers accounted for only 1.3-6.5 per cent of such patients despite a comparatively higher national smoking prevalence of 14-26 per cent in these countries.
This peculiar finding has prompted theories that tobacco smoking (nicotine) could protect against Covid-19 by perhaps blocking viral entry into our human (host) cells or by attenuating inflammatory changes in our lungs through the nicotinic-cholinergic receptor.
In France, researchers hope to test this hypothesis with a randomized trial to evaluate the efficacy of nicotine patches in protecting frontline healthcare workers.
Whilst this may be plausible, it is important such findings are interpreted with caution as data from retrospective observational studies often have inherent bias due to other unadjusted variables.
A simple observation, correlation or association is very different from actual causation hence it is wise not to over conclude.
Covid-19 is a highly infectious disease that predominantly affects our airways and lungs. Smoking has been shown to increase the risk for and severity of numerous respiratory infections and diseases by impairing both our lung physiology and immune system.
The disproportionately low incidence of smokers observed could easily be attributed to incomplete or inaccurate data collection on smoking status amidst an emerging and overwhelming epidemic.
Patients might be too sick or fearful to provide an honest or coherent report of tobacco use.
Furthermore in most countries including Malaysia, smoking prevalence generally declines in the elderly, the very population cohort that is more likely to require hospitalization for a Covid-19 illness.
Scientifically there is conflicting evidence on the precise effects of smoking on the angiotensin converting enzyme-2 (ACE-2), which is the critical host entry point for the coronavirus.
Studies suggest smoking increases expression and upregulation of ACE-2 receptors in the lungs thereby giving the SARS-CoV-2 coronavirus abundant entry points to invade, replicate and cause harm. Logically smokers would have a greater odds of a more severe Covid-19 infection due to the higher viral load.
Smokers however are also more likely than non-smokers to have concomitant co-morbid risk factors (like pre-existing hypertension or underlying respiratory disease) that itself could also contribute to a worse outcome.
The perils of second-hand or passive smoking is evident as it accounts for more than 7,000 lung cancer deaths each year in non-smoking Americans and increases the risk of developing a lung cancer by 20-30 percent.
Amidst this global pandemic, a new added concern relates to whether smokers can be silent spreaders given the high smoking prevalence (43 per cent) in adult Malaysian males and the fact that the vast majority of Covid cases (85 per cent) are asymptomatic.
The habit of smoking involves repetitive hand to mouth actions and habitual heavy smokers are more prone to coughing and less likely to wear facemasks effectively.
The exhaled puff from an infected but asymptomatic smoker can exacerbate viral spread through aerosolisation and airborne transmission.
With a phased relaxation of the movement controlled order (MCO), it is imperative that local authorities ensure the nationwide smoking ban at eateries and other public places remains strictly enforced to protect non-smokers and children from passive smoke and possible viral contamination.
Tobacco kills in excess of 8 million people globally each year with an estimated 2.3 million deaths from
this region.
It is a leading but preventable cause of cardiovascular and respiratory diseases and many cancers including lung cancer.
The World Health Organization designates the May 31 each year as World No Tobacco Day. This year's theme "Protecting youth from industry manipulation and preventing them from tobacco and nicotine use" is most apt.
It is disingenuous for the media or tobacco companies to spin the narrative that tobacco smoking may have a protective effect against Covid-19 in the absence of any compelling evidence.
On the contrary there is emerging evidence that smokers face a greater risk and worse outcomes once infected. Nevertheless, in the spirit of good medical science, the outcome of that planned French nicotine patch trial is much awaited.
The writer is a a cardiothoracic surgeon and President of Lung Cancer Network Malaysia
The views expressed in this article are the author's own and do not necessarily reflect those of the New Straits Times