Smoking Increases COVID-19 Severity and Associated Death Risk

Smoking is likely to worsen the severity of COVID-19 and the risk of dying from the infection, finds a large UK Biobank study published in the respiratory journal Thorax. The evidence on whether smoking is associated with a likelihood of more severe COVID-19 infection has been inconsistent. To strengthen this evidence, this study pool on information from observational and genetic data on smoking and COVID-19.

Several studies have been carried out early in the pandemic that reported a lower prevalence of active smokers among people admitted to hospital with COVID-19 than in the general population.

Other population-based studies have suggested that smoking is a risk factor for the infection. However, most of the studies has been observational in nature and so unable to establish a causal effect.

Therefore, this new study combined observational and Mendelian randomization analyses to understand the relationship better.

Mendelian randomization is a technique that uses genetic variants as proxies for a particular risk factor. In this case genetic variants that make someone more likely to smoke or to smoke more heavily can obtain genetic evidence in support of a causal relationship.

They drew on linked primary care records, COVID-19 test results, hospital admissions data and death certificates to look for associations between smoking and COVID-19 infection severity from January to August 2020 in 421,469 participants of the UK Biobank.

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They all had had their genetic make-up analysed when they agreed to take part in 2006-10.

During the study period, 13446 (3.2%) people took a COVID-19 swab (PCR) test, 1649 (0.4%) of whom tested positive; 968 (0.2%) required admission to hospital; and 444 (0.1%) died as a result of their infection.

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Most (59%) participants had never smoked; over a third (37%) were former smokers; and only 4% were current smokers. Among current smokers, most (71%) were light or moderate smokers (1-19 cigarettes/day); only 29% were heavy smokers (20+/day).

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.

Mendelian randomization technique revealed that a genetic predisposition to smoking was associated with a 45% higher risk of infection and a 60% higher risk of hospital admission for COVID-19.

It also showed that a genetic predisposition to smoke more heavily was associated with a more than doubling in the risk of infection; a 5-fold increase in the risk of hospital admission; and a 10-fold increase in the risk of death from the virus.

Researchers acknowledge that they relied only on hospital COVID-19 test data rather than representative community data but there are similar findings in both sets of analyses.

According to the observational and Mendelian randomization analyses associations with recent smoking behaviors, lifelong predisposition to smoking and smoking heaviness support a causal effect of smoking on COVID-19 severity.

“The idea that tobacco smoking may protect against COVID-19 was always an improbable one,” assert Drs Anthony Laverty and Christopher Millet of Imperial College London, in a linked editorial.

This study strongly suggest that smoking is related to severe COVID-19 risk, and it is good time to quit cigarettes and smoking.



Source-Medindia