The effects of male age on sperm DNA damage in healthy non-smokers

BACKGROUND: The trend for men to have children at older ageraises concerns that advancing age may increase the productionof genetically defective sperm, increasing the risks of transmittinggerm-line mutations. METHODS: We investigated the associationsbetween male age and sperm DNA damage and the influence of severallifestyle factors in a healthy non-clinical group of 80 non-smokers(mean age: 46.4 years, range: 22–80 years) with no knownfertility problems using the sperm Comet analyses. RESULTS:The average percentage of DNA that migrated out of the spermnucleus under alkaline electrophoresis increased with age (0.18%per year, P = 0.006), but there was no age association for damagemeasured under neutral conditions (P = 0.7). Men who consumed>3 cups coffee per day had 20% higher percentage tail DNAunder neutral but not alkaline conditions compared with menwho consumed no caffeine (P = 0.005). CONCLUSIONS: Our findingsindicate that (i) older men have increased sperm DNA damageassociated with alkali-labile sites or single-strand DNA breaksand (ii) independent of age, men with substantial daily caffeineconsumption have increased sperm DNA damage associated withdouble-strand DNA breaks. DNA damage in sperm can be convertedto chromosomal aberrations and gene mutations after fertilization,increasing the risks of developmental defects and genetic diseasesamong offspring.