Kade Patanavanich and I published a meta-analysis that concluded that a history of smoking was associated with COVID-19 disease progression in August 2020 that was based on 19 papers. We just published an update, “Smoking is associated with worse outcomes of COVID-19 particularly among younger adults: a systematic review and meta-analysis” based on 46 papers. The results confirmed our earlier finding that smoking was associated with COVID-19 disease progression and added the conclusions that a history of smoking was also associated with increased risk of death. There is also evidence that the effects of smoking on disease progression are higher among younger patients.
The journal took a very long time to find reviewers, so peer review took a long time. In the meantime two other groups published meta-analyses based on more studies (Simons et al and Zhang et al) that reached consistent conclusions.
Here is the abstract:
Background: Smoking impairs lung immune function and damages upper airways, increasing risks of contracting and severity of infectious diseases. This paper quantifies the association between smoking and COVID-19 disease progression. Methods: We searched PubMed and Embase for studies published from January 1–May 25, 2020. We included studies reporting smoking behavior of COVID-19 patients and progression of disease, including death. We used random effects meta-analysis, meta-regression and locally weighted regression and smoothing to examine relationships in the data. Results: We identified 46 peer-reviewed papers with a total of 22,939 COVID-19 patients, 5421 (23.6%) experienced disease progression and 2914 (12.7%) with a history of smoking (current and former smokers). Among those with a history of smoking, 33.5% experienced disease progression, compared with 21.9% of non-smokers. The metaanalysis confirmed an association between ever smoking and COVID-19 progression (OR 1.59, 95% CI 1.33–1.89, p = 0.001). Ever smoking was associated with increased risk of death from COVID-19 (OR 1.19, 95% CI 1.02–1.39, p = 0.003). We found no significant difference (p = 0.864) between the effects of ever smoking on COVID-19 disease progression between adjusted and unadjusted analyses, suggesting that smoking is an independent risk factor for COVID-19 disease progression. We also found the risk of having COVID-19 progression higher among younger adults (p = 0.001), with the effect most pronounced among younger adults under about 45 years old. Conclusions: Smoking is an independent risk for having progression of COVID-19, including mortality. The effects seem to be higher among young people. Smoking prevention and cessation should remain a priority for the public, physicians, and public health professionals during the COVID-19 pandemic.
The full citation is: Patanavanich R, Glantz S. Smoking is associated with worse outcomes of COVID-19 particularly among younger adults: a systematic review and meta-analysis” BMC Public Health 2021; 21:1554 https://doi.org/10.1186/s12889-021-11579-x. It is available for free here.