Abstract
Researchers believe that smoking might increase the severity of infections caused by SARS-CoV-2 by altering the viability and integrity of the BBB, while promoting the expression of ACE2 in endothelial cells, glia, and neurons. Moreover, as smoking increases the blood circulatory level of VWF and decreases the levels of thrombomodulin, it can lead to dysregulated blood homeostasis and hence, increased risk of thrombosis which significantly increases the risk of stroke and cardiovascular disorders. However, despite current controversies and remarkable study limitations, a recent systematic review and meta-analysis claims that the findings of 18 recent COVID-19 clinical and epidemiological studies show that smokers were statistically less likely to be hospitalized. The authors state that their observations might be due to the effects of nicotine. We believe that the lower number of hospitalized smokers than expected, if confirmed by further studies, can be due to the higher concentration of deposited energy of alpha particles emitted from radionuclides such as Po-210 in cigarette tobacco. The anti-inflammatory effects of localized radiation energy deposition of alpha particles as well as the effect of low doses of radiation on reducing the risk of thrombosis, are possibly involved in the lower number of hospitalized smokers than expected.