Key Takeaways

Smoking is associated with leukocytosis.

As a general rule the increase in white blood cell count is modest (<20%), with the total WBC count rarely exceeding 20 x 109/L.

All white blood cell (WBC) subtypes are affected, but the predominant effect is on neutrophils. 

There is a dose response such that WBC counts are higher in heavy vs. lighter smokers. 

Smoking cessation leads to a time-dependent reversal of leukocytosis, though there is a residual effect even years after stopping.   

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