Smokers are 60% to 80% more likely to be admitted to hospital with COVID-19 and also more likely to die from the disease, a study by Oxford University and other researchers in the United Kingdom suggests, writes Linda Geddes forThe Guardian. In South Africa, a public health specialist told BusinessLive that the study has made an important contribution to scientists’ understanding of smoking and severe COVID-19 outcomes.
The study from Oxford, the University of Bristol and the University of Nottingham, pooled observational and genetic data on smoking and COVID-19 in order to strengthen the evidence base.
It contradicts research published at the start of the pandemic suggesting that smoking might help to protect against the virus. This was later retracted after it was discovered that some of the paper’s authors had financial links to the tobacco industry.
Other studies on whether smoking is associated with a greater likelihood of more severe COVID-19 infection have produced inconsistent results, according to The Guardian report published on 28 September 2021.
One problem is that most of these studies have been observational, making it difficult to establish whether smoking is the cause of any increased risk, or whether something else is to blame, such as smokers being more likely to come from a lower socio-economic background.
Dr Ashley Clift at the University of Oxford and colleagues drew on GP health records, COVID-19 test results, hospital admissions data and death certificates to identify associations between smoking and COVID-19 severity from January to August 2020 in 421,469 participants of the UK Biobank study – all of whom had also previously had their genetic makeup analysed.
Compared with those who had never smoked, current smokers were 80% more likely to be admitted to hospital and significantly more likely to die from COVID-19 if they became infected, continues Linda Geddes in The Guardian.
Clift and his team used a technique called Mendelian randomisation, which uses genetic variants as proxies for a particular risk factor – in this case genetic variants that contribute to whether someone is more likely to smoke or to smoke heavily – to obtain further evidence for a causal relationship.
“The study adds to our confidence that tobacco smoking does not protect against COVID-19, as their Mendelian randomisation analyses are less susceptible to confounding than previous observational studies,” wrote Dr Anthony Laverty and Professor Christopher Millett of Imperial College London in a linked editorial in Thorax.
Link to the full report in The Guardian below.
Smokers ‘significantly’ more likely to die from COVID-19
A story by Tamar Kahn, published by BusinessLive on 28 September 2021, quotes Waasila Jassat, a public health specialist from the National Institute for Communicable Diseases, as say that the study has made an important contribution to scientists’ understanding of smoking and severe COVID-19 outcomes.
“The study is methodologically strong, uses large databases and reaches a congruent finding from two different analytical approaches, that point to the causal effect of smoking on the risk of severe COVID-19,” she said.
While there was increasing evidence of an association between smoking and poor COVID-19 outcomes, there was nevertheless some conflicting evidence, Jassat said.
For example, research on Long COVID in SA found smoking was protective against persistent symptoms one month after COVID-19 hospitalisation. The Long COVID study has yet to be published.
Link to the report in BusinessDay below.
Study details
Smoking and COVID-19 outcomes: an observational and Mendelian randomisation study using the UK Biobank cohort
Ashley K Clift, Adam von Ende, Pui San Tan, Hannah M Sallis, Nicola Lindson, Carol AC Coupland, Marcus R Munafò, Paul Aveyard, Julia Hippisley-Cox and Jemma C Hopewell.
Author affiliations: University of Oxford, University of Bristol and University of Nottingham in the United Kingdom.
Published by Thorax on 27 September 2021.
Abstract
Conflicting evidence has emerged regarding the relevance of smoking on risk of COVID-19 and its severity.
Methods
We undertook large-scale observational and Mendelian randomisation (MR) analyses using UK Biobank.
Most recent smoking status was determined from primary care records (70.8%) and UK Biobank questionnaire data (29.2%). COVID-19 outcomes were derived from Public Health England SARS-CoV-2 testing data, hospital admissions data, and death certificates (until 18 August 2020).
Logistic regression was used to estimate associations between smoking status and confirmed SARS-CoV-2 infection, COVID-19-related hospitalisation, and COVID-19-related death.
Inverse variance-weighted MR analyses using established genetic instruments for smoking initiation and smoking heaviness were undertaken (reported per SD increase).
Results
There were 421,469 eligible participants, 1649 confirmed infections, 968 COVID-19-related hospitalisations and 444 COVID-19-related deaths.
Compared with never-smokers, current smokers had higher risks of hospitalisation (OR 1.80, 95% CI 1.26 to 2.29) and mortality (smoking 1–9/day: OR 2.14, 95% CI 0.87 to 5.24; 10–19/day: OR 5.91, 95% CI 3.66 to 9.54; 20+/day: OR 6.11, 95% CI 3.59 to 10.42).
In MR analyses of 281 105 White British participants, genetically predicted propensity to initiate smoking was associated with higher risks of infection (OR 1.45, 95% CI 1.10 to 1.91) and hospitalisation (OR 1.60, 95% CI 1.13 to 2.27).
Genetically predicted higher number of cigarettes smoked per day was associated with higher risks of all outcomes (infection OR 2.51, 95% CI 1.20 to 5.24; hospitalisation OR 5.08, 95% CI 2.04 to 12.66; and death OR 10.02, 95% CI 2.53 to 39.72).
Interpretation
Congruent results from two analytical approaches support a causal effect of smoking on risk of severe COVID-19.
BusinessLive story – Smokers ‘signicantly’ more likely to die from COVID-19 (Restricted access)
See also from the MedicalBrief archives
SAMRC to implement South Africa’s First Global Tobacco Adult Survey
Emergency attendance for COPD dropped during SA lockdown, tobacco ban
Anti-tobacco group wants ‘balance’ in vaping policies and media coverage
Did COVID-19 stress and uncertainty stall anti-smoking push?