High blood viscosity is closely associated with cigarette smoking and markedly reduced by smoking cessation.

BACKGROUND: Cigarette smoking is an independent risk factor for cardiovascular events such as myocardial infarction and stroke. To date, a useful and convenient method of predicting such events in smokers has not been established. The rheological properties of blood assessed by the microchannel method reflect the blood's viscosity and the state of microthrombus formation, which may predict cardiovascular thrombotic events. METHODS AND RESULTS: Blood fluidity was assessed in 74 smoking patients (54 men, 20 women, mean age 57.9 years) by measuring the blood passage time (BPT) in an aliquot (100 µl) of blood using the Micro Channel Array Flow Analyzer. BPT was significantly related with smoking variables such as daily consumption of tobacco (r = 0.236, P = 0.044), Brinkman's index (r = 0.252, P = 0.033), the Fagerstrom Test for Nicotine Dependence (r = 0.257, P = 0.029), and the score of a self-rating depression scale (r = 0.236, P < 0.05). Multivariate regression analysis revealed that an independent BPT determinant was daily consumption of tobacco (r = 0.326, P = 0.045). Furthermore, smoking cessation markedly decreased BPT from 63.0 s to 49.7 s (P = 0.002) at 3 months after the start of therapy. CONCLUSIONS: Unfavorable blood rheology is closely associated with cigarette smoking and may reflect increased cardiovascular risk in smokers. The study results also suggest that such risk can be reduced after only 3 months of smoking cessation.