Heavy smokers are 48 percent more likely to develop serious health conditions from Covid infections.
That finding from a joint study by two leading local universities prompted researchers to urge smoking cessation services to reduce people's risk of developing serious Covid
Researchers from the medical schools at the University of Hong Kong and Chinese University used a lifetime smoking index from a previous genetic study to assess the correlation between smoking and risk from Covid
-19 infections. The index captures aspects of smoking such as heaviness, duration and initiation from a large genetic summary data of genome-wide association studies. A higher lifetime smoking index implies heavier smoking behavior throughout one's lifetime.
The researchers found a causal link between smoking and the risk of contracting Covid
-19. A higher lifetime smoking index increases the likelihood of contracting a Covid
-19 infection, both mild and severe, by 19 percent, while the risk of contracting severe Covid
increases by 48 percent.
However, researchers said reduced lung function and chronic obstructive pulmonary disease - known detrimental effects of smoking - did not explain the relation between smoking and Covid
Apart from the physiological role of smoking in Covid
, they said, the higher risk in observational studies could be due to other factors such as a lower socioeconomic status, limited living space and access to facilities - which hinder people's adherence to social distancing policies - or the habit exposing smokers to infections when they do so in public places.
Ryan Au Yeung Shiu-lun, an assistant professor at HKU's division of epidemiology and biostatistics at the school of public health, said that apart from the known consequences of smoking such as poor health and a reduced lifespan, the study's findings further prove the importance of smoking cessation by finding a causal link with the risk of contracting Covid
"From a public health perspective, highlighting Covid
-19 as another harm associated with smoking behavior could be explored to further enhance the uptake of smoking cessation services amongst smokers, or reduce the initiation of smoking amongst non-smokers," Au Yeung said, adding it would not only curb the number of Covid
cases in the community but also improve overall population health.
Chinese University assistant professor Kwok Kin-on of the school of public health and primary care said although the databases used for this study are predominantly related to European populations, it is unlikely that the detrimental effect of smoking on Covid
-19 risk differs among other ethnic populations.
"Smokers are at a higher risk of contracting Covid
and are more likely to have severe symptoms, which is why it is imperative for them to receive Covid
-19 vaccination as soon as possible."