Evaluation of DNA damage in leukocytes of ex-smokers by single cell gel electrophoresis

Mutat Res. 1997 Apr 29;375(2):117-23. doi: 10.1016/s0027-5107(97)00007-9.


Single cell gel electrophoresis (SCGE), or comet assay, appears to be a promising tool to estimate DNA damage at the single cell level and it provides information on the presence of damage among individual cells. A follow-up study of 90 smokers who ceased smoking was undertaken to determine the possible decrease of DNA damage in their leukocytes. Before beginning the trial, volunteers smoked on average 26.1 +/- 8.4 cigarettes/day. Comet length did not correlate with the number of cigarettes/day or with the condensate tar content. At the end of the study, 28 volunteers had abandoned the trial, 40 volunteers relapsed into smoking at different times, but with a reduced number of cigarettes/day, whereas 22 fully succeeded in smoking cessation. Throughout the 5 sampling times, a great variability of comet length at individual level was found. However, after 1 year of follow-up, comet length means were found to be significantly shorter (p < 0.0001) in those volunteers who completely quit smoking compared to those who relapsed into smoking (27.2 +/- 1.6 vs. 31.9 +/- 5.1 microns, respectively), irrespective of the amount of cigarettes previously smoked. No effect of age or sex was found. Six months later, these results were confirmed by a further study carried out on a reduced sample of volunteers. The present data strongly suggest that, in spite of the great variability observed, 1 year of smoking cessation is associated with a significant reduction of DNA damage in circulating leukocytes.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Carbon Monoxide / analysis
  • DNA Damage*
  • DNA Mutational Analysis / methods*
  • Electrophoresis, Agar Gel / methods
  • Follow-Up Studies
  • Humans
  • Leukocytes / chemistry*
  • Middle Aged
  • Mutagenicity Tests / methods*
  • Smoking*
  • Time Factors


  • Carbon Monoxide