Dramatic decline in circulating intercellular adhesion molecule-1 concentration on quitting tobacco smoking

The concentration of soluble ICAM-1 (sICAM-1) is significantly elevated in smokers, but it is unclear if smoking is the direct cause of elevated sICAM-1 levels, if the relationship between smoking and sICAM-1 level is dose-dependent, and if smoking cessation may lead to a decline in sICAM-1. We sought to clarify the relationship between smoking and sICAM-1 in a group of smokers who quit smoking for 1 year (n = 30) and a control group who continued to smoke (n = 30). A dose-dependent relationship between plasma sICAM-1 concentration and daily cigarette consumption (P = 0.02), plasma cotinine level (P = 0.02), and expired CO level (P = 0.007) was observed at baseline (n = 60). The mean change in sICAM-1 concentration after 52 weeks was greater for quitters than for continuing smokers (mean difference = -71.1 ng/ml, P < 0.001). The influence of smoking on sICAM-1 needs to be carefully considered in clinical trials. Soluble ICAM-1 remains bioactive and may contribute to pathogenic processes; therefore, reduction in the concentration of circulating ICAM-1 molecules may directly contribute to the health benefits associated with smoking cessation.