The status of global DNA methylation in the spermatozoa of smokers and non-smokers.

Research Question: Does regular smoking affect semen quality and the levels of DNA methylation in mature human spermatozoa?

Design: Spermatozoa from 109 men were evaluated (55 smokers and 54 non-smokers). DNA was extracted from purified spermatozoa, and DNA methylation was quantified by enzyme-linked immunosorbent assay (ELISA).

Results: Global DNA methylation of non-smokers is significantly lower (P < 0.