GSTM1 and polycythemia: However, this study did not find a significant correlation between the amount of cigarette consumption each day and the amount of variation in different blood parameters.[22,23] It is evident from previous studies that the increase of Carboxy Hb among cigarette and shisha smokers leads to the development of polycythemia through an increase of Hb levels secondary to acquired hypoxemia.[24] Moreover, this study conducted in India by Khan et al described how shisha smokers were presented with higher levels of Hb compared to nonsmokers.