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The Health | june-july, 2020
| Hot Topic |
Covid-19: Smoking,
blood thinners
and our lungs –
what’s the score?
Cardiothoracic surgeon and Lung Cancer
Network Malaysia President Dr Anand
Sachithanandan explains how Covid-19
may affect our lungs, the possible effects
of smoking relating to the virus and the
importance of blood thinners
How
SARS-CoV-2
binds to the
human cell
The SARS CoV2
coronavirus which
is responsible
for Covid-19, predominantly
but not exclusively targets our
respiratory system (airways and
lungs).
Recent observations from
China, USA and France curiously suggest
that smokers were less prevalent amongst
patients hospitalised with Covid-19 (only
1.3-6.5 per cent) compared with the national
smoking prevalence (14-32 per cent) in these
countries.
Some researchers have even
hypothesised that the nicotine in
tobacco smoke could paradoxically
protect against Covid-19. It is either by
preventing the SARS CoV-2 coronavirus
from binding to the cellular entry point
ACE-2 receptor in the lungs or by some
form of immunomodulation through the
nicotinic cholinergic receptor to attenuate
the hyper-inflammatory response that
occurs in a severe Covid-19 illness from an
over-activation of our immune response.
While both theories remain plausible, Dr
Sachithanandan cautioned, it was essential
to evaluate the data carefully as these were
retrospective observational studies with
inherent unadjusted bias and small patient
numbers.
Smoking is generally more prevalent in
the lower socioeconomic strata of society
who often lack affordable access to hospital
care. Similarly, smoking prevalence declines
in the elderly, who are most likely to require
hospitalisation.
Furthermore, amidst an evolving and
overwhelming pandemic, patients may
have been too sick or fearful to report their
tobacco use honestly. Dr Sachithanandan
suggested the under-representation
of ‘active or current’ smokers among
hospitalised Covid-19 patients may be an
under-reporting.
He cited data from several single
institutional studies and at least two
pooled meta-analysis which showed that
once infected, smokers were more likely to
develop a severe Covid-19 illness and have
worse outcomes, including admission to the
intensive care unit, mechanical ventilation
or death.
Dr Sachithanandan, however,
acknowledged data analysis could be
complicated as smokers often had
Breathing Easy
concomitant comorbidities
like hypertension, diabetes
or underlying lung disease
that could itself cause a worse outcome.
Preliminary local data suggested the
prevalence of smokers among Malaysians
who died from Covid-19 (20 per cent) was
reasonably similar to the national smoking
prevalence here (22 per cent).
Dr Sachithanandan added contemporary
studies suggested tobacco-smoking
increased the expression or upregulation
of ACE-2 receptors in the lungs. It thereby
provided the coronavirus with more entry
points into the human host cell and better
opportunity to invade, replicate and cause
harm.
The higher viral load may correlate with a
more severe illness. Ferthermore in general,
chronic smoking damages the lungs and
immune system; hence smokers may have
less ‘pulmonary reserve’ to overcome an
acute viral disease like Covid-19.
New hazard of passive smoking
As to whether smokers may be silent
spreaders, Dr Sachithanandan said the
jury was still out. The known mode of viral
transmission was through close contact
and airborne transmission (eg inhalation of
respiratory droplets and aerosolisation).
The habit of smoking involves repetitive
hand-to-mouth manoeuvres; hence
smokers are more likely to touch their
face. Smokers may also be more prone to
coughing and less likely to wear facemasks
effectively.
Following a deep ‘puff’ if a smoker, who
was an asymptomatic carrier, exhaled and
blew out, this could theoretically exacerbate
viral contamination and spread through
The habit of smoking involves
repetitive hand-to-mouth
manoeuvres; hence smokers are more
likely to touch their face. Smokers
may also be more prone to coughing
and less likely to wear facemasks
effectively.”
aerosolisation and airborne transmission.
Dr Sachithanandan added local authorities
should be aware of this potential new hazard
of passive smoking and ensure the smoking
ban was strictly enforced at eateries to
protect children and non-smokers from
second-hand smoke.
Smoking aside, Dr Sachithanandan
shared globally doctors had greatly
improved their understanding of Covid-19
induced lung damage as the pandemic
evolved. In severe cases, we now recognise
this is more than just acute respiratory
distress syndrome (ARDS) which may
necessitate ventilation.
We now understand that there is
disruption to the coagulation (clotting)
system and lining of the blood vessels
(endothelium) with mini clots (micro
thrombosis) occurring in the small blood
vessels (capillaries) in the lungs which
worsens gas exchange (ventilationperfusion
mismatch). Blood thinners or
anticoagulation are truly life-saving in such
cases. — The Health